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Abstract:

A display device includes an illumination unit that delivers a first
light, a second light and a third light. The display also includes a
driving circuit that supplies a pixel with a first data signal for
displaying a first image by illuminating the first light, the driving
circuit supplying the pixel with a second data signal for displaying a
second image by illuminating the second light, the driving circuit
supplying the pixel with a third data signal for displaying a third image
by illuminating the third light.

Claims:

1. A display device, comprising: an illumination unit that delivers a
first light, a second light and a third light; and a driving circuit that
supplies a pixel with a first data signal for displaying a first image by
illuminating the first light, the driving circuit supplying the pixel
with a second data signal for displaying a second image by illuminating
the second light, the driving circuit supplying the pixel with a third
data signal for displaying a third image by illuminating the third light,
the first light having a first color, the first color being white, the
second having a second color other than white, the third light having a
third color, the third color being white, and at least two of: i) a first
period in which the first light is delivered by the illumination unit,
ii) a second period in which the second light is delivered by the
illumination unit, and iii) a third period in which the third light is
delivered by the illumination unit, having lengths that are mutually
different.

2. The display device according to claim 1, the third color being a color
other than the second color.

3. The display device according to claim 1, the illumination unit further
delivering a fourth light, the fourth light having a fourth color, and
the fourth color being a color other than the first color, the second
color and the third color.

4. The display device according to claim 1, the first period being longer
than the second period.

5. The display device according to claim 3, the first period being longer
than a fourth period in which the fourth light is delivered by the
illumination unit.

6. The display device according to claim 1, the first light being
illuminated during an entirety of the first period, the second light
being illuminated during an entirety of the second period, and the third
light being illuminated during an entirety of the third period.

7. A display device, comprising: an illumination unit that delivers a
plurality of lights, the display device being configured such that: the
display device display an image during a frame by using the plurality of
lights; a first light of the plurality of lights being delivered during a
first period included in the frame; a second light of the plurality of
lights being delivered during a second period included in the frame; a
third light of the plurality of lights being delivered during a third
period included in the frame; at least two of: i) the first period, ii)
the second period, and iii) the third period, having lengths that are
mutually different; the first light having a first color, the first color
being white; the second light having a second color other than white; and
the third light being a light having a third color, the third color being
white.

8. The display device according to claim 7, the first period being one
sub-field included in the frame, the second period being one sub-field
included in the frame, and the third period being one sub-field included
in the frame.

9. The display device according to claim 7, the first period being longer
than the second period.

10. The display device according to claim 7, the first light being
delivered during an entirety of the first period, the second light being
delivered during an entirety of the second period, and the third light
being delivered during an entirety of the third period.

11. The display device according to claim 7, a length of the first period
being different from a length of the third period.

12. The display device according to claim 7, the second color being any
one of a red, a green, a blue, a cyan, a magenta and a yellow.

13. An electronic apparatus comprising the display device according to
claim 7.

14. The display device according to claim 7, a length of the second
period being equal to a length of the third period.

15. The display device according to claim 7, the second period coming
after the third period and before the first period.

16. The display device according to claim 7, the plurality of lights
including a fourth light, the fourth light having a fourth color, and the
fourth color being other than the first color, the second color and the
third color.

17. The display device according to claim 16, the plurality of lights
including a fifth light, the fifth light being a light having a fifth
color, and the fifth color being other than the first color, the second
color, the third color, and the fourth color.

18. The display device according to claim 16, the fourth period coming
after the third period and before the first period.

19. The display device according to claim 17, the fourth period and the
fifth period coming after the third period and before the first period.

Description:

[0001] This is a Division of application Ser. No. 12/099,549 filed Apr. 8,
2008. The disclosure of the prior application is hereby incorporated by
reference herein in its entirety.

BACKGROUND

[0002] 1. Technical Field

[0003] The present invention relates to a technique for displaying an
image in a field-sequential scheme.

[0004] 2. Related Art

[0005] In the technical field of a field-sequential display device, an
image problem of the separate perception of a plurality of primary color
components (e.g., a red color component, a green color component, and a
blue color component) at an edge portion of a moving image arises. When
such an image problem occurs, the moving image is represented in mixed
colors that are obtained as a result of the mixture of the plurality of
these primary color components. The field-sequential display device
displays a single-color image of each of these primary color components
in a time-divided sequential manner so as to enable an observer to
perceive a color image. The above-identified image problem due to
primary-color-component separation is hereafter referred to as a "color
breakup".

[0006] In an attempt to address such a technical problem, JP-A-2002-169515
discloses a technique that reduces a color breakup by displaying a
single-color image of each of a white component and a plurality of color
components, both of which are extracted from a plurality of primary color
components, in a sequential manner. As another related art,
JP-A-2005-316092 discloses a technique that reduces a color breakup by
displaying single-color images of colors different from one another in
three regions of an image display area. In the above-identified
JP-A-2005-316092, these three regions are divided at the interval of
predetermined number of rows out of the image display area.

[0007] As still another related art, JP-A-2006-243223 teaches a technique
that decreases display brightness as the percentage of the number of
pixels (i.e., window size) for which high gradation is specified relative
to an entire display image increases. In the related art of
JP-A-2006-243223, if the gradation of a display image is high when viewed
as a whole, the brightness of a display device is decreased so as to
reduce power consumption. On the other hand, according to the related
technique described in JP-A-2006-243223, the brightness of a display
device is increased for an image in which minute high-gradation picture
elements are interspersed against a low-gradation background, for
example, when an image of a firework is displayed. Since the brightness
of the display device is increased when displaying such a type of an
image, each of the minute picture elements is displayed in a clear
manner.

SUMMARY

[0008] In the aforementioned related art described in JP-A-2002-169515,
the gradation of the single-color image of the white component is
significantly higher (which means a significantly higher brightness) than
that of the single-color images of other color components especially if
the display color of an image is close to white. As a consequence
thereof, an observer perceives conspicuous flickers, which is an image
problem, because a plurality of single-color images having gradations
different from one another are displayed in a sequential manner. In order
to address the above-identified problem without any limitation thereto,
the invention aims, as a first aspect thereof, to provide a technical
solution to the image problem of flickers that are attributable to the
displaying of a single-color image of a white component performed by a
field-sequential display device.

[0009] The invention provides, as the first aspect thereof, a display
device that includes: a separating section that generates a separation
image signal, which specifies the gradations of a plurality of color
components (which is a broad generic concept that means either primary
color components or a combination of primary color components and mixed
color components) and the gradations of a plurality of white components,
from an input image signal, which specifies the gradations of a plurality
of primary color components for each of a plurality of pixels; and a
displaying section that displays a single-color image corresponding to
one of the color components and the white components sequentially on the
basis of the generated separation image signal in each of a plurality of
subfields allocated in a frame in such a manner that subfields
corresponding to each of the plurality of the white components are
distanced from each other or one another on a time axis. In the
configuration of a display device according to the first aspect of the
invention described above, it is preferable that the displaying section
should have a liquid crystal device, where the liquid crystal device has
an OCB mode liquid crystal that is sealed in a gap formed between a first
substrate and a second substrate thereof.

[0010] In the configuration of a display device according to the first
aspect of the invention described above, since the single-color images of
a plurality of white components are displayed in split subfields that are
distanced from each other or one another on a time axis, in comparison
with a configuration in which a single-color image of a white component
is displayed in only one subfield, it is possible to achieve a more
suppressed gradation (i.e., brightness) for each of the single-color
images of the white components. Therefore, it is possible to reduce
flickers due to the displaying of a single-color image of a white
component.

[0011] In a specific configuration of a display device according to the
first aspect of the invention described above, the order of displaying
the single-color images of color components and white components is not
restrictively specified herein. For example, it is preferable that the
displaying section should display a single-color image of a white
component in each of subfields that are allocated before and after a
plurality of subfields during which single-color images of the plurality
of the color components are displayed. As another example thereof, it is
preferable that the displaying section should display a single-color
image of a white component in a subfield that is interposed at a gap
allocated in a plurality of subfields during which single-color images of
the plurality of the color components are displayed. With such a
preferred configuration, it is possible to make harder for an observer to
perceive a color breakup image problem.

[0012] In a specific configuration of a display device according to the
first aspect of the invention described above, it is preferable that a
black image should be displayed during a predetermined time period
allocated in a frame. With such a preferred configuration, a color
breakup is reduced because it shortens a time period during which
single-color images of color components are displayed. In addition
thereto, a moving-picture blur is also reduced because it shortens a time
period during which single-color images of color components and
single-color images of white components are displayed. Herein, "a black
image should be displayed" means that the displaying of a color image is
suspended. For example, assuming that the displaying section is made up
of an illumination device and a liquid display device, a black-image
display state refers to an operating condition in which at least one of
the following two are executed: the emission of light from the
illumination device is suspended (i.e., light off) and/or the
transmission factor of each pixel of the liquid crystal device is reduced
to the minimum value. In the preferred configuration described above, it
is further preferable that a black image should be displayed during the
last time period allocated in a frame.

[0013] In a specific configuration of a display device according to the
first aspect of the invention described above, the displaying section
displays a single-color image of at least one white component among the
plurality of white components in a subfield that has a sub-field time
period longer than that of each of subfields during which the
single-color images of the color components are displayed. With the
above-described configuration, since a sufficient time period for the
displaying of single-color images of color components and single-color
images of white components is secured, it is possible to effectively
reduce flickers.

[0014] In a specific configuration of a display device according to the
first aspect of the invention described above, the separating section
generates the separation image signal in such a manner that the plurality
of color components include but not limited to a mixed color component
formed as a result of the mixture of two of the plurality of primary
color components with each other. With the above-described configuration,
in comparison with a configuration in which single-color images of
primary color components are displayed in a successive manner, it becomes
harder for a user who observes the display screen thereof to perceive the
color-breakup image problem. In a further preferred configuration
thereof, a mixed-color-component subfield(s) during which a single-color
image of a mixed color component is displayed is interposed between
primary-color-component subfields during which single-color images of
primary color components are displayed.

[0015] The invention provides, as the first aspect thereof, a method for
driving a display device, the driving method including: generating a
separation image signal, which specifies the gradations of a plurality of
color components and the gradations of a plurality of white components,
from an input image signal, which specifies the gradations of a plurality
of primary color components for each of a plurality of pixels; and
commanding the display device to display a single-color image
corresponding to one of the color components and the white components
sequentially on the basis of the generated separation image signal in
each of a plurality of subfields allocated in a frame in such a manner
that subfields corresponding to each of the plurality of the white
components are distanced from each other or one another on a time axis.
The above-described method for driving a display device offers the same
advantageous effects as those offered by a display device according to
the first aspect of the invention described above.

[0016] In the aforementioned related art described in JP-A-2005-316092,
three regions that constitute the divided portions of an image display
area are arrayed along the column orientation (i.e., vertical direction)
only. With such a configuration, it is practically impossible or at best
difficult to prevent the occurrence of a color breakup if a visual point
of a user who observes the display screen thereof moves in row
orientation (i.e., horizontal direction). In order to address the
above-identified problem without any limitation thereto, the invention
aims, as a second aspect thereof, to provide a technical solution to the
image problem of a color breakup that is attributable to the movement of
a visual point of an observer during display performed by a
field-sequential display device.

[0017] The invention provides, as the second aspect thereof, a display
device that includes: a displaying section that has an array of a
plurality of unit display areas along a first direction and a second
direction that intersect with each other; and a controlling section that
performs control so that a single-color image of each of a plurality of
colors should be displayed sequentially in each of the above-mentioned
more than one unit display areas in such a manner that single-color
images of the plurality of colors are displayed in each of the unit
display areas in a frame. In the configuration of a display device
according to the second aspect of the invention described above, since a
plurality of unit display areas in each of which a single-color image of
each of a plurality of colors is displayed sequentially are arrayed along
a first direction and a second direction that intersect with each other,
it is possible to prevent the occurrence of a color breakup even when a
visual point of an observer moves across a border (or borders) between
the unit display areas in either the first direction or the second
direction. In the configuration of a display device according to the
second aspect of the invention described above, it is preferable that the
displaying section should have a liquid crystal device, where the liquid
crystal device has an OCB mode liquid crystal that is sealed in a gap
formed between a first substrate and a second substrate thereof.

[0018] In a specific configuration of a display device according to the
second aspect of the invention described above, the plurality of unit
display areas make up a rectangular display area as a whole; and the
dimension of each of the unit display areas measured along at least one
of the first direction and the second direction is not greater than the
length of the base of an isosceles triangle that has the vertex angle of
10 degrees and further has the height equal to the length of a short side
of the rectangular display area multiplied by six. As a more preferable
modified configuration of the above, the dimension of each of the unit
display areas measured along at least one of the first direction and the
second direction should not be greater than the length of the base of an
isosceles triangle that has the vertex angle of 10 degrees and further
has the height equal to the length of a short side of the rectangular
display area multiplied by three. With either one of these
configurations, it is possible to prevent the occurrence of a color
breakup due to the movement of a visual point of an observer from one
unit display area. In the configuration of a display device according to
the second aspect of the invention described above, it is preferable that
the number of the unit display areas (and the dimension of each unit
display area) should be determined in such a manner that the cycle of
single-color image display in the plurality of unit display areas equals
a cycle corresponding to a predetermined frame frequency.

[0019] In a specific configuration thereof, it is preferable that a
display device according to the second aspect of the invention described
above should further include an image processing section that generates a
separation image signal that specifies the gradation of a white component
and the gradations of a plurality of color components from an input image
signal that specifies the gradations of a plurality of primary color
components for each of a plurality of pixels, wherein the controlling
section commands the displaying section to display a single-color image
of the white component and a single-color-image of each of the plurality
of color components on the basis of the generated separation image
signal. With such a preferred configuration, since a single-color image
of a white component that is extracted from the display color of a pixel
is displayed, it becomes harder for a user who observes the display
screen thereof to perceive a color breakup image problem in comparison
with a configuration in which single-color images of primary color
components only are displayed. Since no color breakup occurs in a white
component, considering from the viewpoint of color-breakup reduction
only, it is not necessary at all to display a single-color image of a
white component in the unit display areas in a sequential manner.
Therefore, it is preferable to adopt a configuration in which the
controlling section performs control so that a single-color image of each
of the plurality of color components should be displayed sequentially in
each of the above-mentioned more than one unit display areas whereas a
single-color image of the white component should be displayed
concurrently in the unit display areas.

[0020] In a specific configuration of a display device according to the
second aspect of the invention described above, it is preferable that a
plurality of white components should be extracted from the display color
of a pixel. In such a preferred configuration of a display device
according to the second aspect of the invention described above, since
the single-color images of a plurality of white components are displayed
in split subfields that are distanced from each other or one another on a
time axis, in comparison with a configuration in which a single-color
image of a white component is displayed in only one subfield, it is
possible to achieve a more suppressed gradation (i.e., brightness) for
each of the single-color images of the white components. Therefore, it is
possible to reduce flickers due to the displaying of a single-color image
of a white component.

[0021] In the preferred configuration of a display device according to the
second aspect of the invention described above, the order of displaying
the single-color images of color components and white components is not
restrictively specified herein. For example, in a specific configuration
of a display device according to the second aspect of the invention
described above, it is preferable that the displaying section should
display a single-color image of a white component in each of subfields
that are allocated before and after a plurality of subfields during which
single-color images of the plurality of the color components are
displayed. As another example thereof, it is preferable that the
displaying section should display a single-color image of a white
component in a subfield that is interposed at a gap allocated in a
plurality of subfields during which single-color images of the plurality
of the color components are displayed. With such a preferred
configuration, it is possible to make harder for an observer to perceive
a color breakup image problem.

[0022] In a specific configuration of a display device according to the
second aspect of the invention described above, the displaying section
displays a single-color image of at least one white component among the
plurality of white components in a subfield that has a sub-field time
period longer than that of each of subfields during which the
single-color images of the color components are displayed. With the
above-described configuration, since a sufficient time period for the
displaying of single-color images of color components and single-color
images of white components is secured, it is possible to effectively
reduce flickers.

[0023] In a specific configuration of a display device according to the
second aspect of the invention described above, it is preferable that a
black image should be displayed, or in other words, display should be
suspended, during a predetermined time period allocated in a frame. With
such a preferred configuration, a color breakup is reduced because it
shortens a time period during which single-color images of color
components are displayed. In addition thereto, a moving-picture blur is
also reduced because it shortens a time period during which single-color
images of color components and single-color images of white components
are displayed. In the preferred configuration described above, it is
further preferable that a black image should be displayed during the last
time period allocated in a frame.

[0024] In a specific configuration of a display device according to the
second aspect of the invention described above, the image processing
section generates the separation image signal in such a manner that the
plurality of color components include but not limited to a mixed color
component formed as a result of the mixture of two of the plurality of
primary color components with each other. With the above-described
configuration, in comparison with a configuration in which single-color
images of primary color components are displayed in a successive manner,
it becomes harder for a user who observes the display screen thereof to
perceive the color-breakup image problem. In a further preferred
configuration thereof, a mixed-color-component subfield(s) during which a
single-color image of a mixed color component is displayed is interposed
between primary-color-component subfields during which single-color
images of primary color components are displayed.

[0025] The invention provides, as the second aspect thereof, a method for
driving a display device that has an array of a plurality of unit display
areas along a first direction and a second direction that intersect with
each other, the driving method including: performing control so that a
single-color image of each of a plurality of colors should be displayed
sequentially in each of the above-mentioned more than one unit display
areas in such a manner that single-color images of the plurality of
colors are displayed in each of the unit display areas in a frame. The
above-described method for driving a display device offers the same
advantageous effects as those offered by a display device according to
the second aspect of the invention described above.

[0026] In the aforementioned related art described in JP-A-2005-316092,
display is suspended in other areas during a time period in which a
single-color image is displayed in one area. This means that a time
period during which a single-color image is displayed in one area does
not overlap a time period during which a single-color image is displayed
in another area. Therefore, there is a problem that is not addressed by
the above-identified patent publication of JP-A-2005-316092 in that it is
practically impossible or at best difficult to ensure a sufficient color
brightness (i.e., luminosity) of an output image in the image display
area viewed as a whole. In order to address the above-identified problem
without any limitation thereto, the invention aims, as a third aspect
thereof, to provide a technical solution to the image problem of reduced
luminosity (i.e., color brightness) in an output image when the image is
displayed in each of the regions of the image display area of a
field-sequential display device.

[0027] The invention provides, as a third aspect thereof, a display device
that includes: a displaying section that has a first unit display area
and a second unit display area; and a controlling section that performs
control so that a single-color image of each of a plurality of colors
should be displayed concurrently in the first unit display area and the
second unit display area in each of a plurality of subfields allocated in
a frame sequentially in such a manner that a single-color image displayed
in the first display area and a single-color image displayed in the
second display area correspond to colors different from each other in
each subfield. In the configuration of a display device according to the
third aspect of the invention described above, since the single-color
images of colors different from each other are displayed concurrently in
the first unit display area and the second unit display area, in
comparison with a configuration in which a single-color image is
displayed sequentially in each of the display areas, it is possible to
ensure the improved luminosity of an output image easily. In the
configuration of a display device according to the third aspect of the
invention described above, it is preferable that the displaying section
should have a liquid crystal device, where the liquid crystal device has
an OCB mode liquid crystal that is sealed in a gap formed between a first
substrate and a second substrate thereof.

[0028] In a specific configuration thereof, it is preferable that a
display device according to the third aspect of the invention described
above should further include an image processing section that generates a
separation image signal that specifies the gradation of a white component
and the gradations of a plurality of color components from an input image
signal that specifies the gradations of a plurality of primary color
components for each of a plurality of pixels, wherein the controlling
section commands the displaying section to display a single-color image
of the white component and a single-color-image of each of the plurality
of color components (i.e., a primary color component and/or a mixed color
component obtained as a result of the mixture of the primary color
components) on the basis of the generated separation image signal. With
the above-described configuration, it is possible to effectively reduce a
color breakup because, in addition to the fact that no color breakup
occurs in the single-color images of white components, the gradations of
color components, which could cause the color-breakup image problem, are
decreased as a result of the extraction of the white components.

[0029] In a specific configuration thereof, it is preferable that a
display device according to the third aspect of the invention described
above should further include an image processing section that generates a
separation image signal that specifies the gradation of a white component
and the gradations of a plurality of color components from an input image
signal that specifies the gradations of a plurality of primary color
components for each of a plurality of pixels, wherein the controlling
section performs control so that, for each of the plurality of color
components, a single-color image of one color for the first display area
and a single-color image of another color different from the
above-mentioned one color for the second display area should be displayed
in each subfield on the basis of the generated separation image signal
whereas, for the white component, a single-color image of the white
component should be displayed concurrently in the first unit display area
and the second unit display area in the same subfield on the basis of the
generated separation image signal. In another specific configuration
thereof, it is preferable that a display device according to the third
aspect of the invention described above should further include an image
processing section that generates a separation image signal that
specifies the gradation of a white component and the gradations of a
plurality of color components from an input image signal that specifies
the gradations of a plurality of primary color components for each of a
plurality of pixels, wherein the controlling section performs control so
that a single-color image of each of the plurality of colors that include
the white component and the plurality of color components should be
displayed in each subfield on the basis of the generated separation image
signal in such a manner that a single-color image displayed in the first
display area and a single-color image displayed in the second display
area correspond to colors different from each other.

[0030] It is preferable that a plurality of white components should be
extracted from the display color of a pixel, though not limited thereto.
In such a preferred configuration of a display device according to the
third aspect of the invention described above, since the single-color
images of a plurality of white components are displayed in split
subfields that are distanced from each other or one another on a time
axis, in comparison with a configuration in which a single-color image of
a white component is displayed in only one subfield, it is possible to
achieve a more suppressed gradation (i.e., brightness) for each of the
single-color images of the white components. Therefore, it is possible to
reduce flickers due to the displaying of a single-color image of a white
component.

[0031] In a specific configuration of a display device according to the
third aspect of the invention described above, the displaying section
displays a single-color image of at least one white component among the
plurality of white components in a subfield that has a sub-field time
period longer than that of each of subfields during which the
single-color images of the color components are displayed. With the
above-described configuration, since a sufficient time period for the
displaying of single-color images of color components and single-color
images of white components is secured, it is possible to effectively
reduce flickers.

[0032] In a preferred configuration of a display device according to the
third aspect of the invention described above, it is preferable that a
black image should be displayed, or in other words, display should be
suspended, during a predetermined time period allocated in a frame. With
such a preferred configuration, a color breakup is reduced because it
shortens a time period during which single-color images of color
components are displayed. In addition thereto, a moving-picture blur is
also reduced because it shortens a time period during which single-color
images of color components and single-color images of white components
are displayed. In the preferred configuration described above, it is
further preferable that a black image should be displayed during the last
time period allocated in a frame.

[0033] In a specific configuration of a display device according to the
third aspect of the invention described above, the image processing
section generates the separation image signal in such a manner that the
plurality of color components include but not limited to a mixed color
component formed as a result of the mixture of two of the plurality of
primary color components with each other. With the above-described
configuration, in comparison with a configuration in which single-color
images of primary color components are displayed in a successive manner,
it becomes harder for a user who observes the display screen thereof to
perceive the color-breakup image problem. In a further preferred
configuration thereof, a mixed-color-component subfield(s) during which a
single-color image of a mixed color component is displayed is interposed
between primary-color-component subfields during which single-color
images of primary color components are displayed.

[0034] In a specific configuration of a display device according to the
third aspect of the invention described above, the displaying section has
a rectangular display area that is made up of an array of a plurality of
unit display areas along a first direction and a second direction that
intersect with each other, the plurality of unit display areas including
the first unit display area and the second unit display area; and the
dimension of each of the unit display areas measured along at least one
of the first direction and the second direction is not greater than the
length of the base of an isosceles triangle that has the vertex angle of
10 degrees and further has the height equal to the length of a short side
of the rectangular display area multiplied by six. As a more preferable
modified configuration of the above, the dimension of each of the unit
display areas measured along at least one of the first direction and the
second direction should not be greater than the length of the base of an
isosceles triangle that has the vertex angle of 10 degrees and further
has the height equal to the length of a short side of the rectangular
display area multiplied by three. With either one of these
configurations, it is possible to prevent the occurrence of a color
breakup due to the movement of a visual point of an observer from one
unit display area.

[0035] The invention provides, as the third aspect thereof, a method for
driving a display device that has a first unit display area and a second
unit display area, the driving method including: performing control so
that a single-color image of each of a plurality of colors should be
displayed concurrently in the first unit display area and the second unit
display area in each of a plurality of subfields allocated in a frame
sequentially in such a manner that a single-color image displayed in the
first display area and a single-color image displayed in the second
display area correspond to colors different from each other in each
subfield. The above-described method for driving a display device offers
the same advantageous effects as those offered by a display device
according to the third aspect of the invention described above.

[0036] When a field-sequential display device is applied to the
aforementioned related art described in JP-A-2006-243223 according to
which the brightness of a display device is controlled in accordance with
the lightness/darkness of a display image, an image problem arises when
the brightness of the display device is high. That is, the aforementioned
color breakup becomes very conspicuous in such a case. In order to
address the above-identified problem without any limitation thereto, the
invention aims, as a fourth aspect thereof, to provide a technical
solution to the image problem of the aforementioned color breakup that
occurs when the brightness of the related-art field sequential display
device is controlled in accordance with the lightness/darkness of a
display image.

[0037] The invention provides, as a fourth aspect thereof, a display
device that includes: a displaying section that displays an image; an
image processing section that generates a separation image signal that
specifies the gradation of a white component and the gradations of a
plurality of color components from an input image signal that specifies
the gradations of a plurality of primary color components for each of a
plurality of pixels; a driving section that commands the displaying
section to display a single-color image of each of the white component
and the plurality of color components in a plurality of subfields
allocated in a frame sequentially; and a brightness controlling section
that decreases the brightness of display performed by the displaying
section as the number of pixels for which high gradation is specified
increases in a display image in a frame. In the configuration of a
display device according to the fourth aspect of the invention described
above, the brightness controlling section controls display brightness.
Therefore, it is possible to achieve high-contrast display with reduced
power consumption. In addition thereto, since a single-color image of a
white component is displayed in the configuration of a display device
according to the fourth aspect of the invention described above, it is
possible to reduce a color breakup.

[0038] In the configuration of a display device according to the fourth
aspect of the invention described above, it is preferable that the image
processing section should generate the separation image signal that
specifies the gradations of the plurality of color components and the
gradations of a plurality of white components; and the driving section
should command the displaying section to display a single-color image of
each of the plurality of color components and the plurality of white
components in the plurality of subfields sequentially in such a manner
that subfields corresponding to each of the plurality of the white
components are distanced from each other or one another on a time axis.
In the configuration of a display device according to the fourth aspect
of the invention described above, since the single-color images of the
plurality of white components are displayed in split subfields that are
distanced from each other or one another on a time axis, in comparison
with a configuration in which a single-color image of a white component
is displayed in only one subfield, it is possible to achieve a more
suppressed gradation (i.e., brightness) for each of the single-color
images of the white components. Therefore, it is possible to reduce
flickers due to the displaying of a single-color image of a white
component.

[0039] The invention provides, as another specific configuration of the
fourth aspect thereof, a display device that includes: a displaying
section that has an array of a plurality of unit display areas; a
controlling section that performs control so that a single-color image of
each of a plurality of colors should be displayed sequentially in each of
the above-mentioned more than one unit display areas in such a manner
that single-color images of the plurality of colors are displayed in each
of the unit display areas in a frame; and a brightness controlling
section that decreases the brightness of display performed by the
displaying section as the number of pixels for which high gradation is
specified increases in a display image in a frame. With the
above-described configuration, it is possible to achieve high-contrast
display with reduced power consumption because the brightness controlling
section controls display brightness. Since a single-color image of each
of a plurality of colors is displayed sequentially in each of the unit
display areas, it is possible to prevent the occurrence of a color
breakup even when a visual point of an observer moves across a border (or
borders) between the unit display areas.

[0040] The invention provides, as another specific configuration of the
fourth aspect thereof, a display device that includes: a displaying
section that has an array of a plurality of unit display areas including
a first unit display area and a second unit display area; a driving
section that performs control so that a single-color image of each of a
plurality of colors should be displayed concurrently in the first unit
display area and the second unit display area in each of a plurality of
subfields allocated in a frame sequentially in such a manner that a
single-color image displayed in the first display area and a single-color
image displayed in the second display area correspond to colors different
from each other in each subfield; and a brightness controlling section
that decreases the brightness of display performed by the displaying
section as the number of pixels for which high gradation is specified
increases in a display image in a frame. With the above-described
configuration, it is possible to achieve high-contrast display with
reduced power consumption because the brightness controlling section
controls display brightness. Moreover, since the single-color images of
colors different from each other are displayed concurrently in the first
unit display area and the second unit display area, in comparison with a
configuration in which a single-color image is displayed sequentially in
each of the display areas, it is possible to ensure the improved
luminosity of an output image easily and also to reduce the
aforementioned color breakup image problem in an effective manner.

[0041] Note that, in the configuration of a display device having the
above-described brightness controlling section, judgment-target pixels
that are used when making a judgment as to whether the brightness
controlling section should decrease display brightness or not may be all
pixels of a display image or, alternatively, some pixels thereof that are
arrayed in a certain area. Or, in other words, all pixels of a display
image may be subjected to a judgment as to whether high gradation is
specified for them or not; or alternatively, some thereof that are
arrayed in a predetermined area only may be used for such a judgment. It
is preferable that the displaying section according to the first, second,
and third modes thereof described above should have a liquid crystal
device, where the liquid crystal device has an OCB mode liquid crystal
that is sealed in a gap formed between a first substrate and a second
substrate thereof.

[0042] In the configuration of a display device according to the
above-described specific examples of the fourth aspect of the invention,
it is preferable that the brightness controlling section should control
the brightness of display for each of the plurality of unit display areas
in such a manner that, as the number of pixels for which high gradation
is specified increases in each of the unit display areas, the brightness
of display in the unit display area is decreased. With such a
configuration, advantageously, it is possible to satisfy both of a
reduction in power consumption and enhancement in contrast in a
compatible manner depending on the content of an image that is displayed
in each of the unit display areas.

[0043] In a specific configuration of a display device according to the
fourth aspect of the invention described above, the displaying section
has a rectangular display area that is made up of an array of a plurality
of unit display areas along a first direction and a second direction that
intersect with each other; and the dimension of each of the unit display
areas measured along at least one of the first direction and the second
direction is not greater than the length of the base of an isosceles
triangle that has the vertex angle of 10 degrees and further has the
height equal to the length of a short side of the rectangular display
area multiplied by six. As a more preferable modified configuration of
the above, the dimension of each of the unit display areas measured along
at least one of the first direction and the second direction should not
be greater than the length of the base of an isosceles triangle that has
the vertex angle of 10 degrees and further has the height equal to the
length of a short side of the rectangular display area multiplied by
three. With either one of these configurations, it is possible to prevent
the occurrence of a color breakup due to the movement of a visual point
of an observer from one unit display area.

[0044] Pixels of each of the above-described aspects of the invention are
embodied as, for example, electro-optical elements (i.e., electro-optic
devices), which change their optical characteristics such as a
transmission factor and brightness, though not limited thereto, as a
result of a certain electric action, which includes but not limited to
the application of an electric field thereto or the supply of an electric
current thereto. A typical example of such an electro-optical element is
a liquid crystal element, which has liquid crystal sealed between a pair
of electrodes thereof. A display device according to any of the
above-described aspects of the invention can be applied to a variety of
electronic apparatuses.

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The invention will be described with reference to the accompanying
drawings, wherein like numbers reference like elements.

[0046]FIG. 1 is a diagram that schematically illustrates an example of
the configuration of a display device according to an exemplary
embodiment A1 of the invention.

[0047]FIG. 2 is a timing chart that schematically illustrates an example
of the timing operation of a display device according to the exemplary
embodiment A1 of the invention.

[0048]FIG. 3 is a flowchart that illustrates an example of processing for
generation of a separation image signal according to the exemplary
embodiment A1 of the invention.

[0049]FIG. 4 is a diagram that schematically illustrates a specific
example of the generation of a separation image signal according to the
exemplary embodiment A1 of the invention.

[0050]FIG. 5 is a diagram that schematically illustrates a specific
example of the generation of a separation image signal according to the
exemplary embodiment A1 of the invention.

[0051] FIG. 6 is a diagram that schematically illustrates an example of
the display of a display device according to the exemplary embodiment A1
of the invention.

[0052]FIG. 7 is a diagram that schematically illustrates an example of
the widths of a color breakup and a moving-picture blur that occur when a
display device of a related art is adopted.

[0053]FIG. 8 is a diagram that schematically illustrates an example of
the widths of a color breakup and a moving-picture blur that occur when a
display device according to the exemplary embodiment A1 of the invention
is adopted.

[0054]FIG. 9 is a diagram that schematically illustrates a specific
example of the generation of a separation image signal according to an
exemplary embodiment A2 of the invention.

[0055]FIG. 10 is a diagram that schematically illustrates a specific
example of the generation of a separation image signal according to an
exemplary embodiment A2 of the invention.

[0056]FIG. 11 is a timing chart that schematically illustrates an example
of the timing operation of a display device according to the exemplary
embodiment A2 of the invention.

[0057]FIG. 12 is a diagram that schematically illustrates an example of
the generation of a separation image signal according to a variation
example of the exemplary embodiments A1 and A2 of the invention.

[0058]FIG. 13 is a timing chart that schematically illustrates an example
of the timing operation of a display device according to a variation
example of the exemplary embodiments A1 and A2 of the invention.

[0059]FIG. 14 is a timing chart that schematically illustrates an example
of the timing operation of a display device according to a variation
example of the exemplary embodiments A1 and A2 of the invention.

[0060]FIG. 15 is a diagram that schematically illustrates an example of
the configuration of a display device according to an exemplary
embodiment B1 of the invention.

[0061] FIG. 16 is a timing chart that schematically illustrates an example
of the timing operation of a display device according to the exemplary
embodiment B1 of the invention.

[0062]FIG. 17 is a diagram that schematically illustrates an example of
the configuration of a display device according to an exemplary
embodiment B2 of the invention.

[0063]FIG. 18 is a timing chart that schematically illustrates an example
of the timing operation of a display device according to the exemplary
embodiment B2 of the invention.

[0064]FIG. 19 is a timing chart that schematically illustrates an example
of the timing operation of a display device according to a variation
example of the exemplary embodiment B2 of the invention.

[0065]FIG. 20 is a timing chart that schematically illustrates an example
of the timing operation, specifically, the sequential order of
single-color images, of a display device according to a variation example
of the exemplary embodiment B2 of the invention.

[0066]FIG. 21 is a diagram that schematically illustrates an example of
the configuration of a display device according to an exemplary
embodiment C1 of the invention.

[0067]FIG. 22 is a diagram that schematically illustrates a division
example of an image display area in the configuration of a display device
according to the exemplary embodiment C1 of the invention, where the
image display area is divided into a plurality of unit display areas.

[0068]FIG. 23 is a timing chart that schematically illustrates an example
of the timing operation of a display device according to the exemplary
embodiment C1 of the invention.

[0069]FIG. 24 is a diagram that schematically illustrates an example of a
color breakup that is perceived by an observer under a comparative
example A.

[0070]FIG. 25 is a diagram that schematically illustrates an example of
advantageous effects offered by a display device according to the
exemplary embodiment C1 of the invention.

[0071]FIG. 26 is a diagram that schematically illustrates an example of
the configuration of a display device according to an exemplary
embodiment C2 of the invention.

[0072]FIG. 27 is a timing chart that schematically illustrates an example
of the timing operation of a display device according to the exemplary
embodiment C2 of the invention.

[0073]FIG. 28 is a diagram that schematically illustrates an division
example of an image display area according to an exemplary embodiment C3
of the invention.

[0074]FIG. 29 is a timing chart that schematically illustrates an example
of the timing operation of a display device according to the exemplary
embodiment C3 of the invention.

[0075]FIG. 30 is a timing chart that schematically illustrates an example
of the timing operation of a display device according to a variation
example of the exemplary embodiment C3 of the invention.

[0076]FIG. 31 is a timing chart that schematically illustrates an example
of the timing operation of a display device according to a variation
example of the exemplary embodiment C3 of the invention.

[0077]FIG. 32 is a timing chart that schematically illustrates an example
of the timing operation of a display device according to a variation
example of the exemplary embodiment C3 of the invention.

[0078]FIG. 33 is a diagram that schematically illustrates an example of
the configuration of a display device according to an exemplary
embodiment D1 of the invention.

[0079]FIG. 34 is a timing chart that schematically illustrates an example
of the timing operation of a display device according to the exemplary
embodiment D1 of the invention.

[0080]FIG. 35 is a flowchart that illustrates an example of the operation
of a coefficient calculation sub-unit according to the exemplary
embodiment D1 of the invention.

[0081]FIG. 36 is a graph that illustrates an example of a brightness
curve according to the exemplary embodiment D1 of the invention.

[0082]FIG. 37 is a diagram that schematically illustrates the principle
of color-breakup perception (comparative example B).

[0084]FIG. 39 is a graph that shows a relationship between the motion
velocity of the eyes of an observer and a frame frequency at which a
color breakup is not perceived by the observer.

[0085]FIG. 40 is a graph that shows a relationship between the moving
amount of a line of sight and the motion velocity of the eyes of an
observer.

[0086]FIG. 41 is a diagram that schematically illustrates a method for
determining the size of a unit display area according to an exemplary
embodiment of the invention.

[0087]FIG. 42 is a timing chart that schematically illustrates an example
of the timing operation of a display device according to a variation
example of the invention.

[0088]FIG. 43 is a diagram that schematically illustrates an example of
the widths of a color breakup and a moving-picture blur that occur when a
display device according to a variation example of the invention is
adopted.

[0089]FIG. 44 is a timing chart that schematically illustrates an example
of the timing operation of a display device according to a variation
example of the invention.

[0090]FIG. 45 is a diagram that schematically illustrates an example of
the widths of a color breakup and a moving-picture blur that occur when a
display device according to a variation example of the invention is
adopted.

[0091]FIG. 46 is a timing chart that schematically illustrates an example
of the timing operation of a display device according to a variation
example of the invention.

[0092]FIG. 47 is a timing chart that schematically illustrates an example
of the timing operation of a display device according to a variation
example of the invention.

[0093]FIG. 48 is a timing chart that schematically illustrates an example
of the timing operation of a display device according to a variation
example of the invention.

[0094]FIG. 49 is a perspective view that schematically illustrates an
example of an electronic apparatus (a personal computer) to which a
display device according to an exemplary embodiment of the invention is
applied.

[0095]FIG. 50 is a perspective view that schematically illustrates an
example of an electronic apparatus (a mobile phone) to which a display
device according to an exemplary embodiment of the invention is applied.

[0096]FIG. 51 is a perspective view that schematically illustrates an
example of an electronic apparatus (a personal digital assistant) to
which a display device according to an exemplary embodiment of the
invention is applied.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0097] With reference to the accompanying drawings, exemplary embodiments
of the invention are explained below. In the following description,
unless otherwise specified, it should be understood that each of the
constituent elements of a display device according to an exemplary
embodiment of the invention which appears more than one time in this
specification has the same operation and function as long as the same
reference numeral are consistently assigned thereto.

Embodiment A1

[0098]FIG. 1 is a diagram that schematically illustrates an example of
the configuration of a display device according to an exemplary
embodiment A1 of the invention. As illustrated in FIG. 1, an image
display device 100 is provided with an illumination device 10, a liquid
crystal device 20, an image-processing unit 40, and a controlling unit
50. The image-processing unit 40 and the controlling unit 50 may be
provided in a single integrated circuit (IC). Or, the image-processing
unit 40 may be embodied as a circuit component of one integrated circuit
whereas the controlling unit 50 may be embodied as a circuit component of
another integrated circuit in a discrete manner.

[0099] The illumination device 10 is provided at the back of the liquid
crystal device 20. The illumination device 10 illuminates the liquid
crystal device 20. The illumination device 10 has a plurality of
light-emitting elements 12 and a light-guiding plate 14, the latter of
which is configured as an optical waveguide board. The plurality of
light-emitting elements 12 is made up of a red light-emitting element
12R, a green light-emitting element 12G, and a blue light-emitting
element 12B, which correspond to three primary colors of R (red), G
(green), and B (blue), respectively. The optical waveguide board 14
guides light that has been emitted thereto from each of the red
light-emitting element 12R, the green light-emitting element 12G, and the
blue light-emitting element 12B toward the liquid crystal device 20. The
red light-emitting element 12R emits red light, that is, light having a
wavelength that corresponds to a red color component. The green
light-emitting element 12G outputs green light, that is, light having a
wavelength that corresponds to a green color component. The blue
light-emitting element 12R outputs blue light, which is light having a
wavelength that corresponds to a blue color component. In actual
implementation of the invention, a light-reflecting plate and a
light-scattering plate are adhered to the light-guiding plate 14 of the
image display device 100. In order to simplify explanation, however,
these light-reflecting plate and light-scattering plate are omitted from
the drawing.

[0100] The liquid crystal device 20 has a pair of a first substrate 21 and
a second substrate 22. The first substrate 21 and the second substrate 22
are provided so as to face each other. Liquid crystal is sealed in a gap
formed between the first substrate 21 and the second substrate 22 that
are provided opposite to each other. It should be noted that the liquid
crystal is not illustrated in the drawing. It is preferable to adopt a
quick-responsive liquid crystal that operates in an OCB (Optically
Compensated Bend) mode, though not limited thereto. A plurality of pixel
electrodes 24 is arrayed in a matrix pattern on a liquid-crystal-side
surface of the second substrate 22. Each of the plurality of pixel
electrode 24 corresponds to a pixel of an image. The orientation, that
is, alignment, of the liquid crystal that is sandwiched between the first
substrate 21 and the second substrate 22 changes in accordance with an
electric potential difference (i.e., voltage difference) between each of
the pixel electrodes 24 and a counter electrode, the latter of which is
provided on a liquid-crystal-side surface of the first substrate 21. Note
that the counter electrode is not illustrated in the drawing. With such a
configuration, the ratio of the amount of light that is transmitted to
the monitoring side of the image display device 100, which is an image
display side thereof, to the entire amount of light that is emitted from
the illumination device is controlled on a pixel-by-pixel basis. In other
words, the transmission factor of each of the plurality of pixel
electrodes 24 is individually controlled.

[0101] The illumination device 10 and the liquid crystal device 20
function in cooperation with each other so as to display a color image.
FIG. 2 is a timing chart that schematically illustrates an example of the
timing operations of the illumination device 10 and the liquid crystal
device 20 according to an exemplary embodiment of the invention. A frame
F that is shown in FIG. 2 is a unit time period (i.e., unitary time
period) that is used for displaying one color image (e.g., full-color
image). As illustrated in FIG. 2, the frame F is time-divided into a
plurality of sub-fields (i.e., subfields) (hereafter may be abbreviated
as SF). In the illustrated embodiment of the invention, one frame F is
time-divided into six sub-fields (i.e., sub-frames), which are denoted as
SF1, SF2, SF3, SF4, SF5, and SF6. The illumination device 10 and the
liquid crystal device 20 sequentially display a plurality of images each
of which corresponds to an individual single color component displayed in
corresponding one of sub-fields SF. That is, the illumination device 10
and the liquid crystal device 20 perform so-called field sequential (FS)
display. In the following description, the above-described image that
corresponds to an individual single color component displayed in each of
sub-fields SF is referred to as a "single-color image". Herein, the term
"single-color" is used in the meaning of "unicolor" or the like. A user
who observes the display screen of the image display device 100 views
these single-color images displayed in the respective sub-fields SF in a
sequential manner. As a result thereof, they (i.e., the user) visually
perceive a color image that is formed as a mixture of these individual
single color components. For this reason, it is not necessary to provide
any coloration layer such as a color filter or the like in the
configuration of the liquid crystal device 20.

[0102] The image-processing unit 40 illustrated in FIG. 1 processes an
input image signal S1 that is supplied thereto from an external device
that is not shown in the drawing. The input image signal S1 is a signal
that specifies the display color of each of a plurality of pixels that
makes up an image. The input image signal S1 individually specifies a
gradation value for each of three primary color components, that is, a
red color component, a green color component, and a blue color component,
which make up the display color of a pixel. That is, the input image
signal S1 individually specifies the gradation G1_R of the red component
(hereafter may be referred to as "R color component" (R component)), the
gradation G1_G of the green component (hereafter may be referred to as "G
color component" (G component)), and the gradation G1_B of the blue
component (hereafter may be referred to as "B color component" (B
component)) for each of the plurality of pixels.

[0103] As illustrated in FIG. 1, the image-processing unit 40 is provided
with a memory circuit 42 and a separation circuit 44. Hereafter, the term
"color separation" is used with no intention to limit the scope of the
invention. The memory circuit 42 is configured as a frame memory that
stores the input image signal S1 for each of the pixels that make up an
image that is displayed in a frame F. The color separation circuit 44
generates a color separation image signal S2 from the input image signal
S1 that has been memorized in the memory circuit 42 and then outputs the
generated color separation image signal S2. The color separation image
signal S2 individually specifies, for each of the plurality of pixels, a
gradation value for each of separated components, which are obtained in
the form of a plurality of primary-color components and a plurality of
white components as a result of the color separation of a display color
that is specified by the input image signal S1. As illustrated in FIG. 1,
the color separation image signal S2 according to the present embodiment
of the invention specifies the gradation G2_W1 of a first white component
and the gradation G2_W2 of a second white component in addition to the
gradation G2_R of the R color component, the gradation G2_G of the G
color component, and the gradation G2_B of the B color component. In the
following description, the first white component may be referred to as
"W1 component", whereas the second white component may be referred to as
"W2 component".

[0104]FIG. 3 is a flowchart that illustrates an example of the
"color-separating" operations of the color separation circuit 44 of the
image-processing unit 40 according to an exemplary embodiment of the
invention. It should be noted that the procedure illustrated in FIG. 3 is
executed for each of pixels that make up an image. As a first step
thereof, the image-processing unit 40 identifies the minimum value Gmin
among the inputted gradation values of three primary color components,
that is, the gradation G1_R of the R component, the gradation G1_G of the
G component, and the gradation G1_B of the B component, which are
individually specified for each of the plurality of pixels by the input
image signal S1 (step S1). In the next step, the image-processing unit 40
makes a judgment as to whether the minimum value Gmin, which was
identified as the smallest in the preceding step S1, is not greater than
a threshold value TH1 or not (step S2). In a typical configuration, the
threshold value TH1 is a preset fixed value. Notwithstanding the
foregoing, the threshold value TH1 may be configured as a variable value
that is, for example, set in accordance with a setting instruction given
by a user or issued from a higher-level master device.

[0105] A non-limiting example of the inputted gradation values of three
primary color components, that is, the gradation G1_R of the R component,
the gradation G1_G of the G component, and the gradation G1_B of the B
component, which are individually specified by the input image signal S1,
is illustrated in each of the left "gradation bar-chart" portion (a) of
FIG. 4 and the left portion (a) of FIG. 5. In a first example of a
display color that is illustrated in the left portion (a) of FIG. 4, the
gradation G1_G of the G component is the smallest among the inputted
gradation values of three primary color components. In this example, the
minimum value Gmin (i.e., G1_G) is smaller than the threshold value TH1.
In a case where the minimum value Gmin is smaller than the threshold
value TH1, an example of which is illustrated in the left portion (a) of
FIG. 4, the image-processing unit 40 generates a color separation image
signal S2 that sets the minimum value Gmin identified in the previous
step S1 as the gradation G2_W1 of the first white component W1 and
further sets zero as the gradation G2_W2 of the second white component W2
(step S3). Then, the image-processing unit 40 subtracts the minimum value
Gmin from each of the inputted gradation values of three primary color
components, that is, the gradation G1_R of the R component, the gradation
G1_G of the G component, and the gradation G1_B of the B component. Then,
the result of subtraction is specified in the color separation image
signal S2 as the separated gradation values of three primary color
components, that is, the gradation G2_R of the R component, the gradation
G2_G of the G component, and the gradation G2_B of the B component (step
S4).

[0106] In the first example of a display color that is illustrated in the
left portion (a) of FIG. 4, the image-processing unit 40 generates the
color separation image signal S2 that sets the gradation G1_G of the G
component specified by the input image signal S1, which is the minimum
value Gmin among the inputted gradation values of three primary color
components, as the gradation G2_W1 of the first white component W1 as
illustrated in the right portion (b) of FIG. 4. Then, the
image-processing unit 40 calculates a difference value between the
gradation G1_R of the R component of the inputted gradation values of
three primary color components and the minimum value Gmin so as to set
the calculated difference value as the gradation G2_R of the R component
of the separated gradation values of three primary color components.
Similarly, the image-processing unit 40 calculates a difference value
between the gradation G1_B of the B component of the inputted gradation
values of three primary color components and the minimum value Gmin so as
to set the calculated difference value as the gradation G2_B of the B
component of the separated gradation values of three primary color
components. It should be particularly noted that the gradation G2_G of
the G component specified in the color separation image signal S2 is zero
because a difference value between the gradation G1_G of the G component
of the inputted gradation values of three primary color components and
the minimum value Gmin is zero, which is mathematically expressed as:

G2--G=G1--G-Gmin=0.

[0107] In a second example of a display color that is illustrated in the
left portion (a) of FIG. 5, the gradation G1_G of the G component is the
smallest among the inputted gradation values of three primary color
components. Unlike the foregoing first example illustrated in the left
portion (a) of FIG. 4, however, in this example, the minimum value Gmin
(i.e., G1_G) is larger than the threshold value TH1. If the result of a
judgment made in the step S2 is NO (an example of such a case is
illustrated in the left portion (a) of FIG. 5), the image-processing unit
40 generates a color separation image signal S2 that sets the threshold
TH1 as the gradation G2_W1 of the first white component W1 and further
sets a difference value between the minimum value Gmin (i.e., G1_G) and
the threshold value TH1 as the gradation G2_W2 of the second white
component W2 (step S5). Then, the image-processing unit 40 subtracts the
minimum value Gmin from each of the inputted gradation values of three
primary color components, that is, the gradation G1_R of the R component,
the gradation G1_G of the G component, and the gradation G1_B of the B
component. Then, the result of subtraction is specified in the color
separation image signal S2 as the separated gradation values of three
primary color components, that is, the gradation G2_R of the R component,
the gradation G2_G of the G component, and the gradation G2_B of the B
component (step S4). Note that the minimum value Gmin can be expressed
as, in this second example, a value obtained as a result of the addition
of the gradation G2_W2 of the second white component W2 to the gradation
G2_W1 of the first white component W1, or in other words, a result of the
addition of the gradation G2_W2 of the second white component W2 to the
threshold value TH1.

[0108] In the second example of a display color that is illustrated in the
left gradation graph of FIG. 5, the image-processing unit 40 generates
the color separation image signal S2 that sets the threshold TH1 as the
gradation G2_W1 of the first white component W1 and further sets a
difference value between the gradation G1_G of the G component specified
by the input image signal S1, which is the minimum value Gmin among the
inputted gradation values of three primary color components, and the
threshold value TH1 as the gradation G2_W2 of the second white component
W2 as illustrated in the right portion (b) of FIG. 5. Then, the
image-processing unit 40 calculates a difference value between the
gradation G1_R of the R component of the inputted gradation values of
three primary color components and the minimum value Gmin so as to set
the calculated difference value as the gradation G2_R of the R component
of the separated gradation values of three primary color components.
Similarly, the image-processing unit 40 calculates a difference value
between the gradation G1_B of the B component of the inputted gradation
values of three primary color components and the minimum value Gmin so as
to set the calculated difference value as the gradation G2_B of the B
component of the separated gradation values of three primary color
components. Note that the gradation G2_G of the G component specified in
the color separation image signal S2 is zero because a difference value
between the gradation G1_G of the G component of the inputted gradation
values of three primary color components and the minimum value Gmin is
zero. As explained above, if the combined gradation of the pre-separation
"white" component (corresponding to W1+W2), or in other words, the
minimum value Gmin, contained in a display color specified by the input
image signal S1 is greater than the threshold value TH1, the
pre-separation white components is split into the first actual white
component W1 and the second actual white component W2 at the boundary of
the threshold value TH1 in the "color separation" process (i.e., white
extraction process).

[0109] The controlling unit 50 illustrated in FIG. 1 is a circuit that
controls the operations of the image display device 10 and the liquid
crystal device 20. The controlling unit 50 is provided with an
illumination-device driving circuit 52, which drives the illumination
device 10, and a liquid-crystal-device driving circuit 54, which drives
the liquid crystal device 20. The circuit mount configuration of the
controlling unit 50 is not restrictively specified herein. For example,
the illumination-device driving circuit 52 may be provided not on the
controlling unit 50 but on the illumination device 10, whereas the
liquid-crystal-device driving circuit 54 may be provided not on the
controlling unit 50 but on the liquid crystal device 20. As another
non-limiting configuration example thereof, the illumination-device
driving circuit 52 and the liquid-crystal-device driving circuit 54 may
be mounted on a single integrated circuit.

[0110] As illustrated in FIG. 2, the illumination-device driving circuit
52 controls the ON/OFF state of each of the plurality of light-emitting
elements 12, that is, the red light-emitting element 12R, the green
light-emitting element 12G, and the blue light-emitting element 12B, in
each of the aforementioned sub-fields SF. Specifically, for example, the
illumination-device driving circuit 52 performs light-emission control so
that the red light-emitting element 12R only should emit light during the
second sub-field SF2. The illumination-device driving circuit 52 performs
light-emission control so that the green light-emitting element 12G only
should emit light during the third sub-field SF3. The illumination-device
driving circuit 52 performs light-emission control so that the blue
light-emitting element 12B only should emit light during the fourth
sub-field SF4. In addition thereto, the illumination-device driving
circuit 52 controls all of the red light-emitting element 12R, the green
light-emitting element 12G, and the blue light-emitting element 12B to
emit light during the first sub-field SF1 and the fifth sub-field SF5. On
the other hand, the illumination-device driving circuit 52 controls all
of the red light-emitting element 12R, the green light-emitting element
12G, and the blue light-emitting element 12B not to emit light during the
sixth sub-field SF6. As a result of light-emission control that is
performed by the illumination-device driving circuit 52 as described
above, light of one of three primary color components is irradiated onto
the liquid crystal device 20 in each of the sub-fields SF2, SF3, and SF4
in a sequential manner. In addition, white light is irradiated onto the
liquid crystal device 20 in the sub-fields SF1 and SF5. On the other
hand, no light is irradiated onto the liquid crystal device 20 in the
sub-field SF6.

[0111] The liquid-crystal-device driving circuit 54 controls the
transmission factor of liquid crystal corresponding to each of the pixel
electrodes 24 in each of the sub-fields SF in accordance with a gradation
value specified by a color separation image signal S2 for each of the
pixels. That is, the liquid-crystal-device driving circuit 54 supplies an
electric potential (i.e., a voltage) that is in accordance with a
gradation value specified by a color separation image signal S2 for each
of the pixels (hereafter referred to as "data electric potential") at the
beginning of each of the sub-fields SF to each of the pixel electrodes 24
corresponding to the pixel. In each of the sub-fields SF during which the
illumination device 10 emits light that corresponds to any one of a
plurality of (i.e., three) primary color components or any one of a
plurality of white components, a data electric potential is set in
accordance with a gradation value specified by a color separation image
signal S2 for the above-mentioned (corresponding) one of the plurality of
primary color components or the above-mentioned one of the plurality of
white components.

[0112] To be more specific, in the second sub-field SF2 during which red
light is irradiated onto the liquid crystal device 20, the
liquid-crystal-device driving circuit 54 supplies a data electric
potential that corresponds to the gradation G2_R of the R component of
each pixel to the corresponding one of the pixel electrodes 24. In like
manner, in the third sub-field SF3 during which green light is irradiated
onto the liquid crystal device 20, the liquid-crystal-device driving
circuit 54 supplies a data electric potential that corresponds to the
gradation G2_G of the G component to each pixel electrode 24, whereas, in
the fourth sub-field SF4 during which blue light is irradiated onto the
liquid crystal device 20, the liquid-crystal-device driving circuit 54
supplies a data electric potential that corresponds to the gradation G2_B
of the B component to each pixel electrode 24. On the other hand, in the
first sub-field SF1 during which white light is irradiated onto the
liquid crystal device 20, the liquid-crystal-device driving circuit 54
supplies a data electric potential that corresponds to the gradation
G2_W1 of the W1 component to each pixel electrode 24. In like manner, in
the fifth sub-field SF5 during which white light is irradiated onto the
liquid crystal device 20, the liquid-crystal-device driving circuit 54
supplies a data electric potential that corresponds to the gradation
G2_W2 of the W2 component to each pixel electrode 24. In the sixth
sub-field SF6 during which the illumination device 10 switches light off
so that no light should be irradiated onto the liquid crystal device 20,
the liquid-crystal-device driving circuit 54 supplies, to each pixel
electrode 24, a data electric potential that reduces the transmission
factor of liquid crystal to the minimum value (e.g., zero). As a result
of data-electric-potential control that is performed by the
liquid-crystal-device driving circuit 54 as described above, a
single-color image corresponding to each component, which is either one
of a plurality of primary color components (R, and B) or one of a
plurality of white components (W1 and W2), is displayed in the
corresponding one of the sub-fields SF. Therefore, as illustrated in FIG.
2, single-color images that respectively correspond to these
field-assigned components of R, G, B, W1, and W2 are displayed in a
field-sequential manner, specifically, in a sequential order of W1, R, B,
and W2 in the illustrated embodiment of the invention. It should be
particularly noted that the sub-fields SF2, SF3, and SF4 during which
single-color images that correspond to three primary color components of
R, G, and B, respectively are displayed are interposed between the
sub-field SF1 during which a single-color image that corresponds to the
first white component W1 is displayed and the sub-field SF5 during which
a single-color image that corresponds to the second white component W2 is
displayed. This means that, because of the presence of a block of the
R-component subfield SF2, the G-component subfield SF3, and the
B-component subfield SF4 that is interposed therebetween, the
W1-component subfield SF1 and the W2-component subfield SF5 are separated
(i.e., distanced) from each other on a time axis. In the last sub-field
SF6, a black (K) image is displayed in each pixel.

[0113] As explained above, in the configuration of the image display
device 100 according to the present embodiment of the invention,
single-color images that correspond to white components (W1 and W2) as
well as single-color images that correspond to primary color components
(R, G, and B) are displayed. Therefore, in comparison with a case where
single-color images that correspond to primary color components (R, and
B) only are displayed, which means that no single-color images that
correspond to white components (W1 and W2) are displayed, the image
display device 100 according to the present embodiment of the invention
makes it possible to achieve a greater reduction in the aforementioned
color-breakup phenomenon in an image visually perceived by a user who
observes the display screen thereof. A detailed explanation as to how the
image display device 100 according to the present embodiment of the
invention reduces the occurrence of the color-breakup image problem is
given below.

[0114] As illustrated in FIG. 6, it is assumed here that a subject image P
that has a rectangular shape moves to the right at a substantially
constant moving speed against a black background. The imaging-target
object P has a horizontal dimension of D. It is further assumed here that
subject image P moves straight along a line L. Under these assumptions, a
change in the display color thereof that is observed on the line L as
time elapses is studied below. FIG. 7 is a diagram that illustrates an
example of a display color change that is observed when a configuration
of the related art in which single-color images that correspond to
primary color components R, G, and B only are displayed is adopted. FIG.
8 is a diagram that illustrates an example of a display color change that
is observed when the configuration of the image display device 100
according to the present embodiment of the invention in which
single-color images that correspond to white components W1 and W2 as well
as single-color images that correspond to primary color components R, G,
and B are displayed is adopted. In each of FIGS. 7 and 8, the vertical
axis represents time. The horizontal axis represents a transverse
position, that is, a position measured in a horizontal direction.

[0115] As illustrated in Each of FIGS. 7 and 8, the imaging-target object
P moves to the right at each point in time of a change from one frame F
to another frame F. In other words, the position of the subject image P
does not change during one frame F. In contrast, a visual point of a user
who observes the display screen thereof, or simply said, observer's eyes,
moves to the right at a substantially constant moving speed in order to
follow the movement of the subject image P. As explained above, the
actual movement of the subject image P differs from the movement of a
visual point of an observer. Therefore, a user perceives a color breakup
in the proximity of the left edge and the right edge of the moving
subject image P. The width CA shown in each of FIGS. 7 and 8 indicates a
range in which a color breakup is perceived at one edge of the subject
image P. In the following description, this is referred to as a "color
breakup width".

[0116] The color breakup width CA increases as a time period during which
single-color images of primary color components are displayed becomes
longer. In comparison with the related-art configuration illustrated in
FIG. 7 in which single-color images that correspond to primary color
components R, G, and B only are displayed, in the configuration of the
image display device 100 according to the present embodiment of the
invention in which single-color images that correspond to white
components W1 and W2 as well as single-color images that correspond to
primary color components R, and B are displayed, the length of time
period for displaying primary-color-component single-color images becomes
shorter by the length of time period for displaying white-component
single-color images. For this reason, if the configuration of the image
display device 100 according to the present embodiment of the invention
is adopted, as illustrated in FIG. 8, the color breakup width CA
indicating a range in which a user perceives a color breakup becomes
smaller in comparison with the related-art color breakup width CA
illustrated in FIG. 7.

[0117] In addition to the above-described color breakup, since the actual
movement of the subject image P differs from the movement of a visual
point of a user, the user perceives a blurred outline of the moving
subject image P. In the following description, this obscure contour
phenomenon is referred to as a "moving-picture blur". The width CB shown
in each of FIGS. 7 and 8 indicates a range in which a moving-picture blur
is perceived at one edge of the subject image P. This is a dimension
indicating a range in which a user perceives a blurred outline of the
moving subject image P. In the following description, this is referred to
as a "moving-picture blur width". The moving-picture blur width CB
increases as a time period during which single-color images of primary
color components or single-color images of white components are displayed
becomes longer. In connection with the above fact, in the configuration
of the image display device 100 according to the present embodiment of
the invention, the sub-field SF6 during which a black image is displayed
is allocated in each frame F in addition to the sub-fields SF2, SF3, and
SF4 during which single-color images that correspond to three primary
color components of R, G, and B respectively are displayed and the
sub-fields SF1 and SF5 during which single-color images that correspond
to the first white component W1 and the second white component W2
respectively are displayed. The sub-field SF6 is a non-image-display
subfield to which a reference numeral K is assigned in the accompanying
drawings. In comparison with the related-art configuration illustrated in
FIG. 7 in which single-color images that correspond to primary color
components R, G, and B only are displayed, in the configuration of the
image display device 100 according to the present embodiment of the
invention in which the sub-field SF6 during which no single-color image
is displayed is allocated in each frame F, the length of time period for
displaying primary-color-component single-color images and
white-component single-color images becomes shorter by the length of time
period of the sub-field SF6. For this reason, if the configuration of the
image display device 100 according to the present embodiment of the
invention is adopted, as illustrated in FIG. 8, the moving-picture blur
width CB indicating a range in which a user perceives a moving-picture
blur becomes smaller in comparison with the related-art moving-picture
blur width CB illustrated in FIG. 7.

[0118] In the aforementioned related art described in JP-A-2002-169515
according to which a single-color image of a white component that is
extracted from a display color specified by an input image signal S1 is
displayed in only one sub-field SF unlike the present embodiment of the
invention, the gradation of the single-color image of the white component
is significantly higher than that of the single-color images of other
color components especially if the display color of an image is close to
white. For this reason, in the aforementioned related art described in
JP-A-2002-169515, an observer perceives conspicuous flickers because
single-color images of primary color components each having a low
gradation and a single-color image of a white component having a high
gradation are displayed in a field-sequential manner. In contrast, in the
configuration of the image display device 100 according to the present
embodiment of the invention, as has already been explained earlier, if
the combined gradation of the pre-separation "white" component
(corresponding to W1+W2), or in other words, the minimum value Gmin,
contained in a display color specified by the input image signal S1 is
greater than the threshold value TH1, the pre-separation white component
is split into the first actual white component W1 and the second actual
white component W2 at the boundary of the threshold value TH1 in the
white extraction process. Then, these split white components are
respectively displayed in separate sub-fields SF that are "time-isolated"
from each other; specifically, the first white component W1 is displayed
in the first sub-field SF1 whereas the second white component W2 is
displayed in the fifth sub-field SF5 in the illustrated configuration
thereof according to the present embodiment of the invention. Therefore,
it is possible to ensure that the gradation (i.e., brightness, or in
other words, luminance) of a single-color image of each split white
component never exceeds the threshold value TH1. This means that a
difference between the gradations of primary-color-component single-color
images and the gradations of white-component single-color images is made
smaller. Therefore, even in a case where an image having a display color
close to white is displayed, the image display device 100 according to
the present embodiment of the invention can make flickers substantially
less conspicuous in comparison with the aforementioned related art
described in JP-A-2002-169515, which is a non-limiting advantage offered
by the present embodiment of the invention.

[0119] In addition to the above-described factor, how much a user
perceives flickers depends also on the cycles of emission of light to the
monitoring side (i.e., observer's side) and on the time percentage of the
emission of light to the monitoring side in the entire time length of one
frame F. In the following description, the frequency of emission of light
to the monitoring side is referred to as a "light-emission frequency",
whereas the ratio of the time length of the emission of light to the
monitoring side to the entire time length of one frame F is referred to
as a "light-emission duty". As a light-emission frequency and/or a
light-emission duty increase, flickers decrease. If the black-image
subfield SF6 is inserted in each frame F in order to provide a technical
solution to the problem of a motion-picture blur explained above while
referring to FIGS. 7 and 8, a light-emission duty becomes lower in
comparison with a case where the black-image subfield SF6 is not inserted
in each frame F. Accordingly, from this particular viewpoint, the
insertion of the black-image subfield SF6 in each frame F acts
unfavorably to increase flickers. On the other hand, the display of split
white components in separate sub-fields SF, specifically, in the
W1-component subfield SF1 and the W2-component subfield SF5 (in the
illustrated configuration of the image display device 100 according to
the present embodiment of the invention), which are distanced from each
other on a time axis, is technically equivalent to the increasing of a
light-emission frequency, which acts favorably to decrease flickers. To
sum up, in the configuration of the image display device 100 according to
the present embodiment of the invention, it is possible to offset an
increase in flickers due to the insertion of a black-image display by a
decrease therein achieved by the time-separated (i.e., "time-distanced")
display of split white components.

Embodiment A2

[0120] Next, an exemplary embodiment A2 of the invention is explained
below. In the foregoing exemplary embodiment A1 of the invention, it is
explained that a display color specified by the input image signal S1 is
separated into a plurality of primary color components and a plurality of
white components. In contrast, the image-processing unit 40 of the image
display device 100 according to the present embodiment of the invention
generates a color separation image signal S2 as a result of the
separation of a display color specified by the input image signal S1 into
a complementary color component that is formed as a result of the mixture
of two primary color components, a plurality of white components, and a
primary color component that remains after the mixture of two primary
color components. In the following description, the above-described
complementary color component that is formed as a result of the mixture
of two primary color components is referred to as a "mixed color
component".

[0121] In addition to the gradation G2_W1 of the first white component W1
and the gradation G2_W2 of the second white component W2 as well as the
gradation G2_R of the R component, the gradation G2_G of the G component,
and the gradation G2_B of the B component, which are the same as those
specified by the color separation image signal S2 generated by the
image-processing unit 40 according to the foregoing embodiment A1 of the
invention, the color separation image signal S2 generated by the
image-processing unit 40 according to the present embodiment A2 of the
invention further specifies the gradation G2_Y of a yellow (Y) component,
the gradation G2_C of a cyan (C) component, and the gradation G2_M of a
magenta (M) component. Hereafter, the yellow component, the cyan
component, and the magenta component may be referred to as a "Y
component", a "C component", and an "M component", respectively. The
yellow component is the mixed color component obtained as a result of the
mixture of the red component and the green component. The cyan component
is the mixed color component obtained as a result of the mixture of the
green component and the blue component. The magenta component is the
mixed color component obtained as a result of the mixture of the blue
component and the red component.

[0122] A non-limiting example of the inputted gradation values of three
primary color components, that is, the gradation G1_R of the R component,
the gradation G1_G of the G component, and the gradation G1_B of the B
component, which are individually specified by the input image signal S1,
is illustrated in each of the left portion (a) of FIG. 9 and the left
portion (a) of FIG. 10. In a first example of a display color that is
illustrated in the left portion (a) of FIG. 9, the gradation G1_R of the
R component is the smallest among the inputted gradation values of three
primary color components. In this example, the minimum value Gmin (i.e.,
G1_R) is smaller than the threshold value TH1. As done in the foregoing
exemplary embodiment A1, in a case where the minimum value Gmin is
smaller than the threshold value TH1, an example of which is illustrated
in the left portion (a) of FIG. 9, the image-processing unit 40 generates
a color separation image signal S2 that sets the minimum value Gmin
identified in the previous step S1 as the gradation G2_W1 of the first
white component W1 and further sets zero as the gradation G2_W2 of the
second white component W2.

[0123] Then, the image-processing unit 40 sets a gradation value for a
mixed color component that is formed as a result of the mixture of two
primary color components among all three thereof, where the
above-mentioned two primary color components are selected so as not to
include the remaining one thereof that has the minimum inputted gradation
value Gmin. For example, in a case where the gradation G1_R of the R
component is identified as the minimum value Gmin, an example of which is
illustrated in the left portion (a) of FIG. 9, the image-processing unit
40 sets a gradation value G2_C for a mixed color component of cyan (C) on
the basis of the gradation G1_G of the G component and the gradation G1_B
of the B component as illustrated in the right portion (b) of FIG. 9. As
understood from the right portion (b) of FIG. 9, the gradation G2_C of
the C component is calculated as a value obtained after the subtraction
of the minimum value Gmin from the smaller one of the gradation G1_G of
the G component and the gradation G1_B of the B component. In the
illustrated example, since the gradation G1_G of the G component is
smaller than the gradation G1_B of the B component, the gradation G2_C of
the C component is calculated by subtracting the minimum value Gmin from
the gradation G1_G of the G component. It should be noted that the
gradation G2_C of the C component is equal to the result of the
subtraction of the gradation G2_W1 of the first white component W1 from
the smaller one of the gradation G1_G of the G component and the
gradation G1_B of the B component, which is, the former in this example.
Next, the image-processing unit 40 sets a gradation value for a primary
color component that remains after the separation, that is, after the
subtraction, of the first white component W1 and the mixed color
component (i.e., the C component in the first example illustrated in FIG.
9). For example, the gradation G2_B of the B component that remains after
the separation of the first white component W1 and the mixed color
component C is set at a value that is calculated as the result of
subtracting both the gradation G2_C of the C component and the minimum
value Gmin (i.e., the gradation G2_W1 of the first white component W1)
from the pre-separation gradation G1_B of the B component. The remaining
gradation G2_B of the B component after the separation is shown in the
right portion (b) of FIG. 9. It should be particularly noted that the
gradations of primary color components that do not remain after the
separation of a mixed color component and the first white component W1
are specified as zero. In addition, it should be further noted that the
gradations of mixed color components that contain the smallest primary
color component whose inputted gradation value constitutes the minimum
value Gmin are also specified as zero. For example, in the first example
shown in FIG. 9, since the gradations of the R component and the G
component do not remain after the separation of the mixed color component
C and the first white component W1, each of the gradation G2_R of the R
component and the gradation G2_G of the G component is set as zero.
Similarly, each of the gradation G2_Y of the mixed color component Y and
the gradation G2_M of the mixed color component M that contain the
smallest primary color component R whose inputted gradation value
constitutes the minimum value Gmin is set as zero.

[0124] On the other hand, in a second example of a display color that is
illustrated in the left portion (a) of FIG. 10, the gradation G1_B of the
B component is the smallest among the inputted gradation values of three
primary color components. Unlike the foregoing first example illustrated
in the left portion (a) of FIG. 9, however, in this example, the minimum
value Gmin (i.e., G1_B) is larger than the threshold value TH1. As done
in the foregoing exemplary embodiment A1, in a case where the minimum
value Gmin is larger than the threshold value TH1, an example of which is
illustrated in the left portion (a) of FIG. 10, the image-processing unit
40 generates a color separation image signal S2 that sets the threshold
TH1 as the gradation G2_W1 of the first white component W1 and further
sets a difference value between the minimum value Gmin (i.e., G1_B) and
the threshold value TH1 as the gradation G2_W2 of the second white
component W2.

[0125] Then, as done in the foregoing first example illustrated in FIG. 9,
the image-processing unit 40 sets a gradation value for a mixed color
component that is formed as a result of the mixture of two primary color
components among all three thereof, where the above-mentioned two primary
color components are selected so as not to include the remaining one
thereof that has the minimum inputted gradation value Gmin. Specifically,
in a case where the gradation G1_B of the B component is identified as
the minimum value Gmin, an example of which is illustrated in the left
portion (a) of FIG. 10, the image-processing unit 40 sets a gradation
value G2_Y for a mixed color component of yellow (Y) on the basis of the
gradation G1_R of the R component and the gradation G1_G of the G
component as illustrated in the right portion (b) of FIG. 10. As
understood from the right portion (b) of FIG. 10, the gradation G2_Y of
the Y component is calculated as a value obtained after the subtraction
of the minimum value Gmin from the smaller one of the gradation G1_R of
the R component and the gradation G1_G of the G component. In the
illustrated example, since the gradation G1_G of the G component is
smaller than the gradation G1_R of the R component, the gradation G2_Y of
the Y component is calculated by subtracting the minimum value Gmin from
the gradation G1_G of the G component. It should be noted that the
gradation G2_Y of the Y component is equal to the result of the
subtraction of a combined white component value (a value calculated as a
result of addition of the gradation G2_W2 of the second white component
W2 to the gradation G2_W1 of the first white component W1) from the
smaller one of the gradation G1_R of the R component and the gradation
G1_G of the G component, which is, the latter in this example. Then, the
image-processing unit 40 sets the gradation G2_R of the R component that
remains after the separation of the first white component W1, the second
white component W2, and the mixed color component Y at a value that is
calculated as the result of subtracting both the gradation G2_Y of the Y
component and the minimum value Gmin from the pre-separation gradation
G1_R of the R component. It should be particularly noted that the
gradations of primary color components that do not remain after the
separation of a mixed color component, the first white component W1, and
the second white component W2 are specified as zero. In addition, it
should be further noted that the gradations of mixed color components
that contain the smallest primary color component whose inputted
gradation value constitutes the minimum value Gmin are also specified as
zero. For example, in the second example shown in FIG. 10, since the
gradations of the G component and the B component do not remain after the
separation of the mixed color component Y, the first white component W1,
and the second white component W2, each of the gradation G2_G of the G
component and the gradation G2_B of the B component is set as zero.
Similarly, each of the gradation G2_C of the mixed color component C and
the gradation G2_M of the mixed color component M that contain the
smallest primary color component B whose inputted gradation value
constitutes the minimum value Gmin is set as zero.

[0126] As illustrated in FIG. 11, each frame F is time-divided into a
plurality of sub-fields. In the illustrated embodiment of the invention,
one frame F is time-divided into nine sub-fields, which are denoted as
SF1, SF2, SF3, SF4, SF5, SF6, SF7, SF8, and SF9. The controlling unit 50
controls the illumination device 10 and the liquid crystal device 20 so
that the illumination device 10 and the liquid crystal device 20 should
display a plurality of images each of which corresponds to an individual
single color component (a primary color component, a mixed color
component, or a white component) whose gradation is specified by the
color separation image signal S2 in corresponding one of the sub-fields
SF1 through SF8 in a field sequential manner.

[0127] The mixed-color subfields SF during which single-color images of
mixed color components are displayed and the primary-color subfields SF
during which single-color images of primary color components are
displayed are arrayed in an alternate order. Specifically, as illustrated
in FIG. 11, the single-color images of the primary color components R, G,
and B are displayed in the sub-fields SF2, SF4, and SF6, respectively,
whereas the single-color images of the mixed color components C, M, and Y
are displayed in the sub-fields SF3, SF5, and SF7, respectively so as to
provide a sequential display as a whole. It should be noted that, in the
mixed-color subfields SF3, SF5, and SF7 during which the single-color
images of the mixed color components C, M, and Y are displayed,
respectively, the illumination-device driving circuit 52 controls all of
the red light-emitting element 12R, the green light-emitting element 12G,
and the blue light-emitting element 12B so that the corresponding two of
the light-emitting elements 12R, 120, and 12B that form a desired mixed
color should emit light in each of these mixed-color subfields SF. For
example, in the third sub-field SF3, the illumination-device driving
circuit 52 commands the light-emitting elements 12G and 12B to
concurrently emit light so as to irradiate mixed light of the C component
onto the liquid crystal device 20.

[0128] The single-color images of a plurality of white components, that
is, the first white component W1 and the second white component W2 in
this embodiment of the invention, are displayed in the first sub-field
SF1 that is allocated immediately before the color-component subfields
SF2 through SF7 during which the single-color images of the primary color
components and the mixed color components are displayed and in the eighth
sub-field SF8 that is allocated immediately thereafter. In the last
sub-field SF9 of each frame F, as done in the foregoing exemplary
embodiment A1, a black image K is displayed in all of pixels. In other
words, display is suspended in the last sub-field SF9.

[0129] The same advantageous effects as those offered by the configuration
of the image display device 100 according to the foregoing exemplary
embodiment A1 of the invention are offered with the configuration of the
image display device 100 according to the present embodiment A2 of the
invention. The aforementioned problem of a color breakup is conspicuous
especially if the single-color images of a plurality of primary color
components are displayed successively on a time axis. In the sub-field
configuration of the image display device 100 according to the present
embodiment A2 of the invention, as has already been explained above, a
mixed-color subfield SF during which the single-color image of a mixed
color component is displayed is interposed each between "otherwise
adjacent" two primary-color subfields SF during each of which the
single-color image of a primary color component is displayed. Therefore,
in comparison with the sub-field configuration of the image display
device 100 according to the foregoing exemplary embodiment A1 of the
invention in which the primary-color subfields SF during each of which
the single-color image of a primary color component is displayed are
arrayed actually adjacent to each other on a time axis (i.e., follows one
after another in a successive manner), it is possible to achieve a
further greater reduction in the aforementioned color-breakup phenomenon
in an image visually perceived by a user who observes the display screen
thereof.

[0130] In each of the foregoing exemplary embodiments A1 and A2 of the
invention, in order to simplify explanation, it is assumed that the first
white component W1 and the second white component W2, that is, two white
components only, are extracted from an inputted display color. However,
the scope of the invention is not limited to such an exemplary
configuration. That is, the number of white components split after the
extraction (i.e., separation) thereof may be arbitrary modified. For
example, three white components W1, W2, and W3 may be extracted from a
display color specified by an input image signal S1. Specifically, if an
inputted image signal S1 specifies an inputted display color that is
illustrated in the left portion (a) of FIG. 12, the image-processing unit
40 generates a color separation image signal S2 that sets the threshold
TH1 as the gradation G2_W1 of the first white component W1 and further
sets a difference value between the threshold value TH2 and the threshold
value TH1 as the gradation G2_W2 of the second white component W2 where
the threshold value TH2 is preset as a value larger than the threshold
value TH1. In addition, in the generated color separation image signal
S2, the image-processing unit further sets a difference value between the
minimum value Gmin (which is G1_B in the illustrated example of FIG. 12)
and the threshold value TH2 as the gradation G2_W3 of the third white
component W3.

[0131] As illustrated in FIG. 13, each frame F is time-divided into seven
sub-fields, which are denoted as SF1, SF2, SF3, SF4, SF5, SF6, and SF7.
The single-color images of the primary color components R, G, and B are
displayed in the sub-fields SF2, SF4, and SF5, respectively, whereas the
single-color images of the first, second, and third white components W1,
W2, and W3 are displayed in the sub-fields SF1, SF3, and SF6,
respectively so as to provide a sequential display as a whole. It should
be noted that the display order, that is, sub-field arrangement order, of
the single-color images of these primary color components and white
components is not restrictively specified herein. As a non-limiting
modification example thereof, as illustrated in FIG. 14, the single-color
images of the primary color components R, G, and B may be displayed in
even sub-fields of SF2, SF4, and SF6, respectively, whereas the
single-color images of the first, second, and third white components W1,
W2, and W3 may be displayed in odd sub-fields of SF1, SF3, and SF5,
respectively so as to provide a sequential display as a whole. Although a
modification example of the foregoing exemplary embodiment A1 of the
invention is explained above, needless to say, the same modification,
that is, the increased split number of white components after or in the
course of color-separation/white-extraction) may be applied to the
foregoing exemplary embodiment A2 of the invention.

Embodiment B1

[0132]FIG. 15 is a diagram that schematically illustrates an example of
the configuration of a display device according to an exemplary
embodiment B1 of the invention. As illustrated in FIG. 15, an image
display device 100 is provided with an illumination device 10, a liquid
crystal device 20, and a controlling unit 50. For the purpose of
illustration, a distance is provided between the illumination device 10
and the liquid crystal device 20 in FIG. 15. However, needless to say,
the illumination device 10 and the liquid crystal device 20 are provided
close to each other in the actual implementation of the invention.

[0133] As shown in FIG. 15, a rectangular image display area 25 of the
liquid crystal device 20 in which images are displayed is made up of two
image display sub-areas G1 and G2. These image display sub-areas G1 and
G2 are demarcated adjacent to each other as viewed in the Y direction. A
plurality of pixel electrodes 24 is arrayed in the image display area 25.
The first-mentioned image display sub-area G1 is subdivided into three of
unit display areas A1a, A1b, and A1c. These unit display areas A1a, A1b,
and A1c are arrayed along the X direction. In the denomination (i.e.,
naming) of "unit display area", the term "unit" is used in the meaning of
"unitary" or the like. Accordingly, the term "unit display area" may be
reworded as "unitary display area" in the following description. In like
manner, the second-mentioned image display sub-area G2 is subdivided into
three of unit display areas A2a, A2b, and A2c. These unit display areas
A2a, A2b, and A2c are also arrayed along the X direction. That is, the
image display area 25 of the liquid crystal device 20 includes these six
unit display areas A1a, A1b, A1c, A2a, A2b, and A2c, which are arrayed in
an X-Y matrix pattern. In the following description, these six unit
display areas A1a, A1b, A1c, A2a, A2b, and A2c are collectively referred
to as "unit display areas A" (unitary display areas A). Each of the unit
display areas A is a rectangular region that has the same dimension as
those of others. The plurality of pixel electrodes 24 is arrayed in an
X-Y matrix pattern in each of the unit display areas A.

[0134] The illumination device 10 illustrated in FIG. 15 is made up of six
area illumination units B1a, B1b, B1c, B2a, B2b, and B2c, which
correspond to the above-mentioned six unit display areas A1a, A1b, A1c,
A2a, A2b, and A2c, respectively. In the denomination of "area
illumination unit", the term "unit" is used in the meaning of "section",
"portion", or the like. Accordingly, the term "area illumination unit"
may be reworded as "area illumination section" in the following
description. In addition, in the following description, these six area
illumination units B1a, B1b, B1c, B2a, B2b, and B2c are collectively
referred to as "area illumination units B" (area-illuminating sections
B). As illustrated in FIG. 15, each of the area-illuminating sections
(i.e., area illumination units) B and the corresponding one of the
unitary display areas (i.e., unit display areas) A overlap each other as
viewed in a direction perpendicular to the X-Y plane of the image display
area 25, that is, in a plan view. For example, the unitary display area
A1a and the area-illuminating section B1a overlap each other in a plan
view. In like manner, the unitary display area A1b and the
area-illuminating section B1b overlap each other in a plan view. The same
holds true for the remaining four sets of the unit display areas A and
the area illumination units B. Accordingly, as illustrated in FIG. 15,
the above-mentioned six area illumination units B are arrayed in an X-Y
matrix pattern.

[0135] Each of the area illumination units B of the illumination device 10
has three light-emitting elements 12 and a light-guiding plate 14, the
latter of which is configured as an optical waveguide board. These three
light-emitting elements 12 are made up of a red light-emitting element
12R, a green light-emitting element 12Q and a blue light-emitting element
12B, which correspond to three primary colors of R, G, and B,
respectively. The optical waveguide board 14 guides light that has been
emitted thereto from each of the red light-emitting element 12R, the
green light-emitting element 120 and the blue light-emitting element 12B
toward the unit display areas A of the liquid crystal device 20. The red
light-emitting element 12R emits red light, that is, light having a
wavelength that corresponds to a red color component. The green
light-emitting element 12G outputs green light, that is, light having a
wavelength that corresponds to a green color component. The blue
light-emitting element 12R outputs blue light, which is light having a
wavelength that corresponds to a blue color component. In actual
implementation of the invention, a light-reflecting plate and a
light-scattering plate are adhered to the light-guiding plate 14 of the
image display device 100. In order to simplify explanation, however,
these light-reflecting plate and light-scattering plate are omitted from
the drawing.

[0136] The illumination device 10 and the liquid crystal device 20
function in cooperation with each other so as to display a color image.
FIG. 16 is a timing chart that schematically illustrates an example of
the timing operations of the illumination device 10 and the liquid
crystal device 20 according to an exemplary embodiment of the invention.
A frame F that is shown in FIG. 16 is a unitary time period that is used
for displaying one color image (e.g., full-color image). The liquid
crystal device 20 displays an image at a frame frequency of 120 Hz, which
is double-speed display. Therefore, the time length of each frame F is
1/120 second.

[0137] In the illustrated embodiment of the invention, each frame F is
time-divided into three sub-fields SF1, SF2, and SF3, which correspond to
three primary color components without any redundancy nor duplication
among them. The illumination device 10 and the liquid crystal device 20
sequentially display the single-color image of a corresponding primary
color component in each of these three sub-fields SF1, SF2, and SF3 that
are allocated in the frame F. That is, the illumination device 10 and the
liquid crystal device 20 perform so-called field sequential display. A
user who observes the display screen of the image display device 100
views these single-color images displayed in the respective sub-fields SF
in a sequential manner. As a result thereof, they (i.e., the user)
visually perceive a color image that is formed as a mixture of these
individual single color components. For this reason, it is not necessary
to provide any coloration layer such as a color filter or the like in the
configuration of the liquid crystal device 20.

[0138] The controlling unit 50 illustrated in FIG. 15 is a circuit that
controls the operations of the image display device 10 and the liquid
crystal device 20. The controlling unit 50 is provided with an
illumination-device driving circuit 52, which drives the illumination
device 10, and a liquid-crystal-device driving circuit 54, which drives
the liquid crystal device 20. As illustrated in FIG. 15, an input image
signal S1 is supplied from an external device that is not shown in the
drawing to the controlling unit 50. The input image signal S1
individually specifies a gradation value for each of three primary color
components, that is, R color component (i.e., R component), G color
component (i.e., G component), and B color component (i.e., B component),
which make up the display color of a pixel.

[0139] As illustrated in FIG. 16, each sub-field SF is further
time-divided into one writing time period PW and three display time
periods P1, P2, and P3. The liquid-crystal-device driving circuit 54 sets
the electric potential (i.e., voltage) of each of the pixel electrodes 24
at a data electric potential that is in accordance with a gradation value
specified by an input image signal S1 for each one of three primary color
components in the writing time period PW of the corresponding sub-field
SF during which the single-color image of the above-mentioned each one
primary color component is displayed.

[0140] To be more specific, for example, the liquid-crystal-device driving
circuit 54 supplies, to each of the pixel electrodes 24, a data electric
potential that is in accordance with a gradation value G1_R specified by
an input image signal S1 for the R component of each pixel in the writing
time period PW of the first sub-field SF1 during which a single-color
image corresponding to the R component is displayed. This operation is
called as "R writing". In like manner, the liquid-crystal-device driving
circuit 54 supplies, to each of the pixel electrodes 24, a data electric
potential that is in accordance with a gradation value G1_G specified by
the input image signal S1 for the G component of each pixel in the
writing time period PW of the second sub-field SF2 during which a
single-color image corresponding to the G component is displayed. The
liquid-crystal-device driving circuit 54 supplies, to each of the pixel
electrodes 24, a data electric potential that is in accordance with a
gradation value G1_B specified by the input image signal S1 for the B
component of each pixel in the writing time period PW of the third
sub-field SF3 during which a single-color image corresponding to the B
component is displayed. These operations are called as "G writing" and "B
writing", respectively. The transmission factors of liquid crystal that
are set during the display time periods P1, P2, and P3 are determined in
accordance with the respective data electric potentials that are set for
the pixel electrodes 24 during the respective writing time periods PW.

[0141] The illumination-device driving circuit 52 illustrated in FIG. 15
controls the ON/OFF state of each of the plurality of light-emitting
elements 12, that is, the red light-emitting element 12R, the green
light-emitting element 12G, and the blue light-emitting element 12B of
each of the aforementioned area illumination units B in a sequential
manner. More specifically, in each of three sub-fields SF during which
the single-color image of the corresponding one of three primary color
components is displayed, the illumination-device driving circuit 52
commands the light-emitting elements 12 of the corresponding one of three
primary color components (i.e., 12R, 12G, or 12B) provided in the
above-mentioned three area illumination units B1a, B1b, and B1c that are
arrayed opposite to the above-mentioned three unit display areas A1a,
A1b, and A1c of the first-mentioned image display sub-area G1,
respectively, to emit light in a sequential manner during the display
time periods P1, P2, and P3, respectively. That is, in this operation,
the illumination-device driving circuit 52 commands three light-emitting
elements 12, which does not mean a set of 12R, 12Q and 12B but means a
group of light-emitting elements 12 of the same primary color component
(R, G, or B) that are separately provided on the above-mentioned three
area illumination units B1a, B1b, and B1c, to emit light during the
display time periods P1, P2, and P3 respectively in such a manner that
light emission does not occur at the same timing among them. In like
manner, in each of three sub-fields SF during which the single-color
image of the corresponding one of three primary color components is
displayed, the illumination-device driving circuit 52 commands the
light-emitting elements 12 of the corresponding one of three primary
color components provided in the above-mentioned three area illumination
units B2b, B2c, and B2a that are arrayed opposite to the above-mentioned
three unit display areas A2b, A2c, and Ata of the second-mentioned image
display sub-area G2, respectively, to emit light in a sequential manner
during the display time periods P1, P2, and P3, respectively. That is, in
this operation, the illumination-device driving circuit 52 commands three
light-emitting elements 12, which does not mean a set of 12R, 12G, and
12B but means a group of light-emitting elements 12 of the same primary
color component that are separately provided on the above-mentioned three
area illumination units B2b, B2c, and B2a, to emit light during the
display time periods P1, P2, and P3 respectively in such a manner that
light emission does not occur at the same timing among them. It should be
noted that, in each of these display time periods P1, P2, and P3, one of
three area illumination units B1 (which correspond to the first-mentioned
image display sub-area G1) that is currently emitting light from the
light-emitting element 12 thereof is not arrayed adjacent to one of three
area illumination units B2 (which correspond to the second-mentioned
image display sub-area G2) that is currently emitting light from the
light-emitting element 12 thereof when viewed along the Y direction.

[0142] A more specific explanation of the above is given now while
referring to FIG. 16. Firstly, an attention is focused on the
first-mentioned three area illumination units B1, which correspond to the
first-mentioned image display sub-area G1. In the first display period P1
of the first sub-field SF1 during which a single-color image
corresponding to the R component is displayed, the light-emitting element
12R of the area illumination unit B1a thereof emits light. Thereafter, in
the second display period P2 of the same first sub-field SF1, the
light-emitting element 12R of the area illumination unit B1b thereof
emits light. Next, in the third display period P3 subsequent to the
second display period P2, the light-emitting element 12R of the area
illumination unit B1c thereof emits light. That is, the light-emitting
element 12R of the area illumination unit B1 emits light in the
sequential order of B1a, B1b, and B1c in the first sub-field SF1 (i.e.,
B1a→B1b→B1c). Next, an attention is focused on the
second-mentioned three area illumination units B2, which correspond to
the second-mentioned image display sub-area G2. In the first display
period P1 of the first sub-field SF1, the light-emitting element 12R of
the area illumination unit B2b thereof emits light. Thereafter, in the
second display period P2 of the same first sub-field SF1, the
light-emitting element 12R of the area illumination unit B2c thereof
emits light. Next, in the third display period P3 subsequent to the
second display period P2, the light-emitting element 12R of the area
illumination unit B2a thereof emits light. That is, the light-emitting
element 12R of the area illumination unit B2 emits light in the
sequential order of B2b, B2c, and B2a in the first sub-field SF1 (i.e.,
B2b→B2c→B2a). In like manner, the light-emitting element
12G of each of these six area illumination units B emits light in a
sequential manner when viewed as a whole in the second sub-field SF2,
whereas the light-emitting element 12B of each of these six area
illumination units B emits light in a sequential manner when viewed as a
whole in the third sub-field SF3.

[0143] Therefore, in each of the display time periods P1, P2, and P3 of
each of the sub-fields SF, the single-color image of the corresponding
one of three primary color components is displayed in two of the
above-described six unit display areas A one of which is not adjacent to
the other in the X direction nor in the Y direction in such a manner that
the above-mentioned two of the unit display areas A switch over (i.e.,
change over) from one display time period P to another display time
period P in a sequential manner. Specifically, for example, as
illustrated in FIG. 16, the single-color image of the R component is
displayed in the unit display areas A1a and A2b during the display time
period P1 of the first sub-frame SF1. Thereafter, the single-color image
of the R component is displayed in the unit display areas A1b and A2c
during the display time period P2 of the first sub-frame SF1.
Subsequently, the single-color image of the R component is displayed in
the unit display areas A1c and Ata during the display time period P3 of
the first sub-frame SF1. In like manner, the single-color image of the G
component is displayed in the corresponding two unit display areas A
during each display time period P of the second sub-frame SF2 in a
sequential manner when viewed as a whole, whereas the single-color image
of the B component is displayed in the corresponding two unit display
areas A during each display time period P of the third sub-frame SF3 in a
sequential manner when viewed as a whole. Therefore, during each frame F,
the single-color images of all three primary color components are
displayed in each of the unit display areas A.

[0144] In the configuration of the image display device 100 according to
the present embodiment of the invention, as explained above, single-color
images are displayed in the unit display areas A during the sub-fields SF
in a sequential manner. With such a configuration, it is possible to
effectively prevent the occurrence of the aforementioned color-breakup
image problem that is attributable to a difference between the actual
movement of a subject image P and the movement of a visual point of a
user. For example, it is assumed here that a visual point of a user who
observes the display screen thereof moves to the left during the display
time period P2 in which a single-color image is displayed in the unit
display area A1b. At this point in time, the display of a single-color
image in the unit display area A1a, which is the "destination" of the
movement of the observer's eyes in the leftward direction from the unit
display area A1b, has already been finished. For this reason, s/he (i.e.,
the observer) perceives no color breakup image problem due to the
movement of his/her visual point. As another example, it is assumed here
that a visual point of a user who observes the display screen thereof
moves downward during the display time period P2 in which a single-color
image is displayed in the unit display area A1b. At this point in time,
the display of a single-color image in the unit display area A2b, which
is the destination of the movement of the user's eyes in the downward
direction from the unit display area A1b, has already been finished. For
this reason, they (i.e., the user) perceive no color breakup image
problem due to the movement of their visual point.

Embodiment B2

[0145] In the foregoing exemplary embodiment B1 of the invention, it is
explained that the single-color images of three primary color components
are sequentially displayed on the basis of an input image signal S1. In
contrast, in the configuration of the image display device 100 according
to the present embodiment of the invention, as done in the foregoing
exemplary embodiment A1 of the invention, a display color specified by
the input image signal S1 is separated into a plurality of primary color
components and a plurality of white components.

[0146]FIG. 17 is a diagram that schematically illustrates an example of
the configuration of a display device according to an exemplary
embodiment B2 of the invention. As illustrated in FIG. 17, the image
display device 100 according to the present embodiment of the invention
is provided with, in addition to the same components as those of the
foregoing exemplary embodiment B1 of the invention, the image-processing
unit 40 as in the configuration of the image display device 100 according
to the foregoing exemplary embodiment A1 of the invention. The
image-processing unit 40 according to the present embodiment of the
invention generates a color separation image signal S2 from an input
image signal S1 that is supplied thereto from an external device that is
not shown in the drawing and then outputs the generated color separation
image signal S2. The color separation image signal S2 individually
specifies, for each of the plurality of pixels, a gradation value for
each of separated components, which are obtained in the form of a
plurality of primary-color components and a plurality of white components
as a result of the color separation of a display color that is specified
by the input image signal S1. As illustrated in FIG. 17, the color
separation image signal S2 according to the present embodiment of the
invention specifies the gradation G2_W1 of the first white component W1
and the gradation G2_W2 of the second white component W2 in addition to
the gradation G2_R of the R color component, the gradation G2_G of the G
color component, and the gradation G2_B of the B color component. The
color separation image signal S2 is generated through the same processing
as that explained above while referring to FIGS. 3, 4, and 5 in the
foregoing first exemplary embodiment A1 of the invention.

[0147]FIG. 18 is a timing chart that schematically illustrates an example
of the timing operation of the image display device 100 according to the
present embodiment of the invention. As illustrated in FIG. 18, each
frame F is time-divided into a plurality of sub-fields. In the
illustrated embodiment of the invention, one frame F is time-divided into
six sub-fields, which are denoted as SF1, SF2, SF3, SF4, SF5, and SF6.
The operations of the illumination device 10 and the illumination-device
driving circuit 52 during the sub-fields SF2, SF3, and SF4 in the present
embodiment of the invention are the same as those during the sub-fields
SF1, SF2, and SF3 in the foregoing exemplary embodiment B1 of the
invention.

[0148] The illumination-device driving circuit 52 according to the present
embodiment of the invention commands all three of red, green, and blue
light-emitting elements 12R, 12G, and 12B provided in each of the area
illumination units B to emit light during each of the first, second, and
third display time periods of P1, P2, and P3 in each of the first
sub-field SF1 and the fifth sub-field SF5. As a result of such
light-emission control that is performed by the illumination-device
driving circuit 52, white light is irradiated onto the liquid crystal
device 20 during each of the first, second, and third display time
periods of P1, P2, and P3 in each of the first sub-field SF1 and the
fifth sub-field SF5. On the other hand, the illumination-device driving
circuit 52 commands all three of the red, green, and blue light-emitting
elements 12R, 12G, and 12B provided in each of the area illumination
units B not to emit light during the sixth sub-field SF6. Therefore, no
light is irradiated onto the liquid crystal device 20 in the sixth
sub-field SF6.

[0149] As done in the foregoing exemplary embodiment B1 of the invention,
the liquid-crystal-device driving circuit 54 according to the present
embodiment of the invention supplies a data electric potential that is in
accordance with a gradation value specified by a color separation image
signal S2 for each of the pixels during the writing time period PW of
each of the sub-fields SF to each of the pixel electrodes 24
corresponding to the pixel. More specifically, in the writing time period
PW of each of the second, third and fourth sub-fields SF2, SF3, and SF4,
the liquid-crystal-device driving circuit 54 supplies, to each of the
pixel electrodes 24, a data electric potential that is in accordance with
the gradation G2_R of the R component, the gradation G2_G of the G
component, and the gradation G2_B of the B component that are specified
in the color separation image signal S2 as the separated gradation values
of three primary color components. On the other hand, in the writing time
period PW of the first sub-field SF1, which is one sub-field during which
white light is irradiated onto the liquid crystal device 20, the
liquid-crystal-device driving circuit 54 supplies a data electric
potential that corresponds to the gradation G2_W1 of the W1 component to
each pixel electrode 24. This operation is called as "W1 writing". In
like manner, in the writing time period PW of the fifth sub-field SF5,
which is another sub-field during which white light is irradiated onto
the liquid crystal device 20, the liquid-crystal-device driving circuit
54 supplies a data electric potential that corresponds to the gradation
G2_W2 of the W2 component to each pixel electrode 24. This operation is
called as "W2 writing". In the sixth sub-field SF6 during which the
illumination device 10 switches light off so that no light should be
irradiated onto the liquid crystal device 20, the liquid-crystal-device
driving circuit 54 supplies, to each pixel electrode 24, a data electric
potential that reduces the transmission factor of liquid crystal to the
minimum value (e.g., zero). This operation is called as "K writing".

[0150] As a result of data-electric-potential control that is performed by
the liquid-crystal-device driving circuit 54 as described above, a
single-color image corresponding to each of a plurality of primary color
components R, and B is displayed in the unit display areas A (i.e., two
unit display areas A during each display time period P) in a sequential
manner when viewed as a whole during the corresponding one of the second,
third, and fourth sub-fields SF2, SF3, and SF4 as displayed so during the
corresponding one of the first, second, and third sub-fields SF1, SF2,
and SF3 in the foregoing exemplary embodiment B1 of the invention. On the
other hand, a single-color image corresponding to each of a plurality of
white components W1 and W2 is displayed in all of the unit display areas
A in a non-sequential manner, that is, at the same time, during the
corresponding one of the first sub-field SF1 and the fifth sub-field SF5.
For this reason, the length of time period during which a single-color
image corresponding to each of the first white component W1 and the
second white component W2 is displayed in all of the unit display areas A
at the same time during the corresponding one of the first sub-field SF1
(W1) and the fifth sub-field SF5 (W2) is greater than the length of time
period during which a single-color image corresponding to each of three
primary color components R, and B is displayed in the unit display areas
A in a sequential manner when viewed as a whole during the corresponding
one of the second, third, and fourth sub-fields SF2 (R), SF3 (G), and SF4
(B) because the former is displayed during all three of the display time
periods P1, P2, and P3 whereas the latter is displayed during only one of
these three display time periods P1, P2, and P3. It should be
particularly noted that the sub-fields SF2, SF3, and SF4 during which
single-color images that correspond to three primary color components of
R, and B, respectively are displayed are interposed between the sub-field
SF1 during which a single-color image that corresponds to the first white
component W1 is displayed and the sub-field SF5 during which a
single-color image that corresponds to the second white component W2 is
displayed. This means that, because of the presence of a block of the
R-component subfield SF2, the G-component subfield SF3, and the
B-component subfield SF4 that is interposed therebetween, the
W1-component subfield SF1 and the W2-component subfield SF5 are separated
(i.e., distanced) from each other on a time axis. In the last sub-field
SF6, a black image K is displayed in each pixel.

[0151] As explained above, in the configuration of the image display
device 100 according to the present embodiment of the invention, since
the first white component W1 and the second white component W2 are
extracted out of a display color of each pixel, the brightness level of a
single-color image of each of three primary color components of R, G, and
B becomes lower in comparison with that of the foregoing exemplary
embodiment B1 of the invention. No color breakup occurs in the
single-color image of a white component. Therefore, in comparison with
the configuration of the image display device 100 according to the
foregoing exemplary embodiment B1 of the invention in which single-color
images that correspond to primary color components R, G, and B only are
displayed, which means that no single-color images that correspond to
white components W1 and W2 are displayed, the image display device 100
according to the present embodiment of the invention makes it possible to
achieve a greater reduction in the aforementioned color-breakup
phenomenon in an image visually perceived by a user who observes the
display screen thereof. In addition, in the configuration of the image
display device 100 according to the present embodiment of the invention,
the non-image-display subfield SF6 during which a black K image is
displayed is allocated in each frame F in addition to the sub-fields SF2,
SF3, and SF4 during which single-color images that correspond to three
primary color components of R, and B respectively are displayed and the
sub-fields SF1 and SF5 during which single-color images that correspond
to the first white component W1 and the second white component W2
respectively are displayed. Therefore, in comparison with the
configuration of the image display device 100 according to the foregoing
exemplary embodiment B1 of the invention in which no black image K is
displayed, the image display device 100 according to the present
embodiment of the invention makes it possible to achieve a greater
reduction in the aforementioned moving-picture blur phenomenon, that is,
the visual perception of the blurred outline of a moving subject image P.

[0152] Moreover, in the configuration of the image display device 100
according to the present embodiment of the invention, as has already been
explained earlier, if the combined gradation of the pre-separation
"white" component (corresponding to W1+W2), or in other words, the
minimum value Gmin, contained in a display color specified by the input
image signal S1 is greater than the threshold value TH1, the
pre-separation white component is split into the first actual white
component W1 and the second actual white component W2 at the boundary of
the threshold value TH1 in the white extraction process. Then, these
split white components are respectively displayed in separate sub-fields
SF that are "time-isolated" from each other; specifically, the first
white component W1 is displayed in the first sub-field SF1 whereas the
second white component W2 is displayed in the fifth sub-field SF5 in the
illustrated configuration thereof according to the present embodiment of
the invention. This means that a difference between the gradations of
primary-color-component single-color images and the gradations of
white-component single-color images is made smaller. Therefore, in
comparison with, for example, the configuration of the aforementioned
related art described in JP-A-2002-169515 according to which a
single-color image of a white component that is extracted from a display
color specified by an input image signal S1 is displayed in only one
sub-field SF, the image display device 100 according to the present
embodiment of the invention has an advantage in that it can reduce
flickers, which is the same non-limiting advantageous effects of the
invention as those offered by the image display device 100 according to
the foregoing exemplary embodiment A1 of the invention. Furthermore, as
is the case with the image display device 100 according to the foregoing
exemplary embodiment A1 of the invention, in the configuration of the
image display device 100 according to the present embodiment of the
invention, it is possible to offset an increase in flickers due to the
insertion of a black-image display by a decrease therein achieved by the
time-separated display of split white components.

[0153] In the above-described example of the configuration of the image
display device 100 according to the present embodiment B2 of the
invention, a single-color image that corresponds to the first white
component W1 is displayed during each of the first, second, and third
display time periods of P1, P2, and P3 of the first sub-field SF1,
whereas a single-color image that corresponds to the second white
component W2 is displayed during each of the first, second, and third
display time periods of P1, P2, and P3 of the fifth sub-field SF5.
However, the scope of the invention is not limited to such an exemplary
configuration. For example, as illustrated in FIG. 19, a single-color
image corresponding to the first white component W1 may be displayed in
the unit display areas A in a sequential manner when viewed as a whole.
The same modified sub-field operation as described above may be applied
to the second white component W2. Although it is technically possible to
adopt the above-described modified configuration, since no color breakup
occurs in a white component as has already been explained above,
considering from the viewpoint of color-breakup reduction only, it is not
necessary at all to display a single-color image of a white component in
the unit display areas A in a sequential manner. In comparison with this
modified sub-field configuration illustrated in FIG. 19 according to
which a single-color image of a white component is not displayed during
all three of the display time periods P1, P2, and P3 in a continuous
manner but displayed during only one of these three display time periods
P in a sequential manner, the above-described sub-field configuration
illustrated in FIG. 18 according to which a single-color image of each of
the white components W1 and W2 is not displayed during only one of these
three display time periods P in a sequential manner but displayed during
all three of the display time periods P1, P2, and P3 in a continuous
manner is more advantageous in that it is possible to decrease the
brightness level, that is, suppress the brightness, of the light-emitting
elements 12 of each of the area illumination units B in the corresponding
white-component subfield SF1 and SF5.

[0154] It should be noted that the order of displaying single-color images
in the unit display areas A is not restrictively specified in the
above-described exemplary embodiments B1 and B2 of the invention. That
is, the display order thereof may be changed arbitrarily. Although it is
explained in the foregoing exemplary embodiment B1 of the invention that
a single-color image of the same color component (in the illustrated
example, the same primary-color component) is displayed throughout the
plurality of unit display areas A in each sub-field SF, a single-color
image of different color components may be displayed throughout the
plurality of unit display areas A (in a sequential manner) in each
sub-field SF as shown in a non-limiting modification example illustrated
in FIG. 20. However, in order to realize the different-color sequential
display illustrated in FIG. 20, it is necessary to extract the gradation
G1_R of the R component, the gradation G1_G of the G component, and the
gradation G1_B of the B component from the input image signal S1 for each
unit display area A. In contrast, such an area-by-area extraction is not
required in the foregoing exemplary embodiment B1 of the invention in
which a single-color image of the same color component is displayed
throughout the plurality of unit display areas A in each sub-field SF.
Therefore, considering from the viewpoint of reduction in the processing
load of the controlling unit 50, the configuration described in the
foregoing exemplary embodiment B1 of the invention is more advantageous.
As has already been explained earlier while referring to FIGS. 12, 13,
and 14, the number of white components split after the extraction thereof
and the display order/positions (i.e., sub-field arrangement
order/positions) of the single-color images of white components are not
restrictively specified herein and thus may be arbitrary modified.

Embodiment C1

[0155]FIG. 21 is a diagram that schematically illustrates an example of
the configuration of a display device according to an exemplary
embodiment C1 of the invention. As illustrated in FIG. 21, an image
display device 100 is provided with an illumination device 10, a liquid
crystal device 20, and a controlling unit 50. For the purpose of
illustration, a distance is provided between the illumination device 10
and the liquid crystal device 20 in FIG. 21. However, needless to say,
the illumination device 10 and the liquid crystal device 20 are provided
close to each other in the actual implementation of the invention.

[0156] As shown in FIG. 21, a rectangular image display area 25 of the
liquid crystal device 20 in which images are displayed is divided into a
plurality of unit display areas A that are arrayed in a matrix pattern
made up of rows that extend in the X direction and columns that extend in
the Y direction in such a manner that these rows and columns intersect
each other. A plurality of pixel electrodes 24 is arrayed in the image
display area 25. Each of the unit display areas A is a rectangular region
that has the same dimension as those of others. The plurality of pixel
electrodes 24 is arrayed in an X-Y matrix pattern in each of the unit
display areas A.

[0157]FIG. 22 is a concept diagram that schematically illustrates a
division example of the image display area 25, where the image display
area 25 is divided into twenty-five unit display areas A that are arrayed
in a matrix pattern made up of five rows that extend in the X direction
and five columns that extend in the Y direction in such a manner that
these five rows and five columns intersect each other. As illustrated in
FIG. 22, the plurality of unit display areas A (in the illustrated
example, twenty-five unit display areas A) that make up the image display
area 25 are divided into three groups C1, C2, and C3. Each individual
group C contains more than one unit display area A. As understood from
the drawing, one unit display area A that belongs to a certain group C is
not adjacent to another unit display area A that belongs to the same
group C as viewed along the X direction nor along the Y direction.

[0158] The illumination device 10 illustrated in FIG. 21 is made up of a
plurality of area illumination units (i.e., area-illuminating sections)
B, which correspond to the above-mentioned plurality of unit display
areas (i.e., unitary display areas) A, respectively. As illustrated in
FIG. 21, each of the area-illuminating sections (i.e., area illumination
units) B and the corresponding one of the unitary display areas (i.e.,
unit display areas) A overlap each other as viewed in a direction
perpendicular to the X-Y plane of the image display area 25, that is, in
a plan view. Accordingly, the plurality of area illumination units B is
arrayed in an X-Y matrix pattern.

[0159] Each of the area illumination units B of the illumination device 10
has three light-emitting elements 12 and a light-guiding plate 14, the
latter of which is configured as an optical waveguide board. These three
light-emitting elements 12 are made up of a red light-emitting element
12R, a green light-emitting element 12G, and a blue light-emitting
element 12B, which correspond to three primary colors of R, G, and B,
respectively. The optical waveguide board 14 guides light that has been
emitted thereto from each of the red light-emitting element 12R, the
green light-emitting element 12G, and the blue light-emitting element 12B
toward the unit display areas A of the liquid crystal device 20. The red
light-emitting element 12R emits red light, that is, light having a
wavelength that corresponds to a red color component. The green
light-emitting element 12G outputs green light, that is, light having a
wavelength that corresponds to a green color component. The blue
light-emitting element 12R outputs blue light, which is light having a
wavelength that corresponds to a blue color component. In actual
implementation of the invention, a light-reflecting plate and a
light-scattering plate are adhered to the light-guiding plate 14 of the
image display device 100. In order to simplify explanation, however,
these light-reflecting plate and light-scattering plate are omitted from
the drawing.

[0160] The illumination device 10 and the liquid crystal device 20
function in cooperation with each other so as to display a color image.
FIG. 23 is a timing chart that schematically illustrates an example of
the timing operations of the illumination device 10 and the liquid
crystal device 20 according to an exemplary embodiment of the invention.
A frame F that is shown in FIG. 23 is a unit time period (i.e., unitary
time period) that is used for displaying one color image (e.g.,
full-color image). The liquid crystal device 20 displays an image at a
frame frequency of 120 Hz, which is double-speed display. Therefore, the
time length of each frame F is 1/120 second.

[0161] As illustrated in FIG. 23, each frame F is time-divided into a
plurality of sub-fields. In the illustrated embodiment of the invention,
one frame F is time-divided into three sub-fields, which are denoted as
SF1, SF2, and SF3. The illumination device 10 and the liquid crystal
device 20 sequentially display a plurality of single-color images, that
is, unicolor images, that correspond to primary color components in the
plurality of unit display areas A in a "time-parallel and concurrent"
manner (hereafter referred to as "parallel") in each of sub-fields SF.
For the definition of the term "time-parallel and concurrent" or
"parallel" that appears in the description of the present embodiment of
the invention, refer to the operation illustrated in FIG. 23. In this
way, the illumination device 10 and the liquid crystal device 20 perform
so-called field sequential display. A user who observes the display
screen of the image display device 100 views these single-color images
displayed in the unit display areas A during the respective sub-fields SF
in a sequential manner. As a result thereof, they visually perceive a
color image that is formed as a mixture of these individual single color
components. For this reason, it is not necessary to provide any
coloration layer such as a color filter or the like in the configuration
of the liquid crystal device 20.

[0162] The controlling unit 50 illustrated in FIG. 21 is a circuit that
controls the operations of the image display device 10 and the liquid
crystal device 20. The controlling unit 50 is provided with an
illumination-device driving circuit 52, which drives the illumination
device 10, and a liquid-crystal-device driving circuit 54, which drives
the liquid crystal device 20. As illustrated in FIG. 21, an input image
signal S1 is supplied from an external device that is not shown in the
drawing to the controlling unit 50. The input image signal S1
individually specifies a gradation value for each of three primary color
components, that is, R color component (i.e., R component), G color
component (i.e., G component), and B color component (i.e., B component),
which make up the display color of a pixel.

[0163] The controlling unit 50 controls the operations of the illumination
device 10 and the liquid crystal device 20 on the basis of the input
image signal S1 so that single-color images that correspond to primary
color components should be sequentially displayed in the unit display
areas A that make up the image display area 25. More specifically, during
a set of the sub-fields SF1, SF2, and SF3 that constitutes one frame F,
the controlling unit 50 commands single-color images of three primary
color components to be displayed sequentially in the plurality of unit
display areas A that make up the image display area 25. That is, as
illustrated in FIG. 23, each of the single-color images of three primary
color components R, and B are displayed once during each frame F in the
sequential order of B, R, G for the unit display areas A that belong to
the first group C1, in the sequential order of R, G, B for the unit
display areas A that belong to the second group C2, and in the sequential
order of G, B, R for the unit display areas A that belong to the third
group C3.

[0164] In addition, as understood from the above explanation and the
drawing, the controlling unit 50 commands single-color images to be
displayed in a parallel manner in all unit display areas A in such a
manner that the display color of a single-color image that appears in the
unit display areas A that belong to one group C differs from the display
color of another single-color image that appears in the unit display
areas A that belong to another group C in each sub-field SF. Therefore,
one unit display area A that displays a single-color image of a certain
color component R, G, or B is not adjacent to another unit display area A
that displays a single-color image of the same color component R, G, or B
as viewed along the X direction nor along the Y direction. If an
attention is focused on the sub-fields SF1, SF2, and SF3, such a
non-adjacent arrangement can be paraphrased as a sub-field configuration
in which, the sequential order of the display colors of single-color
images that appear in the unit display areas A that belong to one group C
differs from the sequential order of the display colors of single-color
images that appear in the unit display areas A that belong to another
group C.

[0165] For example, as illustrated in FIG. 23, during the first sub-field
SF1, the single-color image of the B component is displayed in each of
the unit display areas A that belong to the first group During the same
first sub-field SF1, the single-color image of the R component is
displayed in each of the unit display areas A that belong to the second
group C2, whereas the single-color image of the G component is displayed
in each of the unit display areas A that belong to the third group C3.
During the second sub-field SF2, the single-color image of the R
component is displayed in each of the unit display areas A that belong to
the first group C1. During the same second sub-field SF2, the
single-color image of the G component is displayed in each of the unit
display areas A that belong to the second group C2, whereas the
single-color image of the B component is displayed in each of the unit
display areas A that belong to the third group C3. During the third
sub-field SF3, the single-color image of the G component is displayed in
each of the unit display areas A that belong to the first group C1.
During the same third sub-field SF3, the single-color image of the B
component is displayed in each of the unit display areas A that belong to
the second group C2, whereas the single-color image of the R component is
displayed in each of the unit display areas A that belong to the third
group C3.

[0166] The liquid-crystal-device driving circuit 54 sets the electric
potential (i.e., voltage) of each of the pixel electrodes 24, which are
arrayed in each of the unit display areas A, at a data electric potential
that is in accordance with a gradation value specified by an input image
signal S1 for a certain primary color component R, G, or B that should be
displayed in the unit display areas A that belong to a certain group in
the writing time period PW of each sub-field SF that is allocated at the
headmost timeslot portion thereof. For example, in the writing time
period PW of the first sub-field SF1, the liquid-crystal-device driving
circuit 54 supplies, to each of the pixel electrodes 24 that are arrayed
in each of the first-group unit display areas A that belong to the group
C1, a data electric potential that is in accordance with a gradation
value G1_B specified by an input image signal S1 for the B component. In
the same writing time period PW of the first sub-field SF1, the
liquid-crystal-device driving circuit 54 supplies, to each of the pixel
electrodes 24 that are arrayed in each of the second-group unit display
areas A that belong to the group C2, a data electric potential that is in
accordance with a gradation value G1_R specified by the input image
signal S1 for the R component, whereas the liquid-crystal-device driving
circuit 54 supplies, to each of the pixel electrodes 24 that are arrayed
in each of the third-group unit display areas A that belong to the group
C3, a data electric potential that is in accordance with a gradation
value G1_G specified by the input image signal S1 for the G component. In
like manner, in the writing time period PW of the second sub-field SF2,
the liquid-crystal-device driving circuit 54 supplies, to each of the
pixel electrodes 24 that are arrayed in each of the first-group unit
display areas A that belong to the group C1, a data electric potential
that is in accordance with a gradation value G1_R specified by the input
image signal S1 for the R component. In the same writing time period PW
of the second sub-field SF2, the liquid-crystal-device driving circuit 54
supplies, to each of the pixel electrodes 24 that are arrayed in each of
the second-group unit display areas A that belong to the group C2, a data
electric potential that is in accordance with a gradation value G1_G
specified by the input image signal S1 for the G component, whereas the
liquid-crystal-device driving circuit 54 supplies, to each of the pixel
electrodes 24 that are arrayed in each of the third-group unit display
areas A that belong to the group C3, a data electric potential that is in
accordance with a gradation value G1_B specified by the input image
signal S1 for the B component. In the writing time period PW of the third
sub-field SF3, the liquid-crystal-device driving circuit 54 supplies, to
each of the pixel electrodes 24 that are arrayed in each of the
first-group unit display areas A that belong to the group C1, a data
electric potential that is in accordance with a gradation value G1_G
specified by an input image signal S1 for the G component. In the same
writing time period PW of the third sub-field SF3, the
liquid-crystal-device driving circuit 54 supplies, to each of the pixel
electrodes 24 that are arrayed in each of the second-group unit display
areas A that belong to the group C2, a data electric potential that is in
accordance with a gradation value G1_B specified by the input image
signal S1 for the B component, whereas the liquid-crystal-device driving
circuit 54 supplies, to each of the pixel electrodes 24 that are arrayed
in each of the third-group unit display areas A that belong to the group
C3, a data electric potential that is in accordance with a gradation
value G1_R specified by the input image signal S1 for the R component.
The transmission factor of liquid crystal, that is, the gradation of a
single-color image for each pixel, that is set during each of the
sub-fields SF1, SF2, and SF3 is determined in accordance with the data
electric potentials that are set for the pixel electrodes 24 during the
writing time period PW thereof.

[0167] The illumination-device driving circuit 52 illustrated in FIG. 21
controls the ON/OFF state of each of the plurality of light-emitting
elements 12, that is, the red light-emitting element 12R, the green
light-emitting element 12G, and the blue light-emitting element 12B of
each of the aforementioned area illumination units B in a sequential
manner during the sub-fields SF. More specifically, the
illumination-device driving circuit 52 controls the illumination device
10 in such a manner that, in each sub-field SF, the illumination device
10 emits light having a wavelength that corresponds to a certain primary
color component from not all but some of the area illumination units B
thereof, specifically, the area illumination units B that are arrayed
opposite to the corresponding (i.e., not all but some of) unit display
areas A at which a single-color image of the above-mentioned certain
primary color component should be displayed in the above-mentioned
sub-field SF. This light-emission control is performed for not one but
all of three primary color components in each sub-field SF. Referring to
the first sub-field SF1 shown in FIG. 23, the illumination-device driving
circuit 52 controls the illumination device 10 in such a manner that the
light-emitting elements 12 of not all but some of the area illumination
units B thereof emit light corresponding to each primary color component.
For example, in the first sub-field SF1, the illumination-device driving
circuit 52 controls the illumination device 10 in such a manner that the
light-emitting elements 12B of the area illumination units B thereof that
are arrayed opposite to the corresponding first-group unit display areas
A that belong to the group C1 emit light. Concurrently therewith, the
illumination-device driving circuit 52 controls the illumination device
10 in such a manner that the light-emitting elements 12R of the area
illumination units B thereof that are arrayed opposite to the
corresponding second-group unit display areas A that belong to the group
C2 emit light, whereas the illumination-device driving circuit 52
controls the illumination device 10 in such a manner that the
light-emitting elements 12G of the area illumination units B thereof that
are arrayed opposite to the corresponding third-group unit display areas
A that belong to the group C3 emit light.

[0168] Since the controlling unit 50 controls the operations of the
illumination device 10 and the liquid crystal device 20 as explained
above, single-color images of color components different from one another
are displayed in a parallel manner in the unit display areas A that
belong to the first, second, and third groups C1, C2, and C3 respectively
in each sub-field SF. Therefore, in comparison with the aforementioned
related-art configuration described in JP-A-2005-316092 according to
which a single-color image is displayed exclusively for each area divided
out of the image display area 25, the configuration of the image display
device 100 according to the present embodiment of the invention is more
advantageous in that it is possible to ensure the enhanced color
brightness (i.e., luminosity) of an output image.

[0169] In addition, since single-color images of color components
different from one another are displayed in a parallel manner in the unit
display areas A, which are divided portions of the image display area 25,
in the configuration of the image display device 100 according to the
present embodiment of the invention, it is possible to achieve a greater
reduction in the aforementioned color-breakup phenomenon in an image
visually perceived by a user who observes the display screen thereof in
comparison with a configuration in which the single-color images of the
same color component are displayed in the entire region of the image
display area 25 during each sub-field SF of a frame F. It should be noted
that such a same-color display configuration is referred to as a
"comparative example A" in the following description. A detailed
explanation as to how the image display device 100 according to the
present embodiment of the invention achieves a greater reduction in the
color-breakup image problem is given below.

[0170] Each of FIGS. 24 and 25 is a concept diagram that schematically
illustrates an example of the formation of a perceived image on the
retinas of an observer as a result of the displaying of a white
imaging-target object (i.e., subject image) P. Note that white is the
mixed color component that is formed as a result of the mixture of all
three primary color components. FIG. 24 corresponds to the comparative
example A, whereas FIG. 25 corresponds to the present embodiment C1 of
the invention. In each of FIGS. 24 and 25, it is assumed that a visual
point of a user who observes the display screen thereof moves to the
right instantaneously. Such an instant movement of a visual point is
called as a saccade, which can be further defined as, simply said, a fast
movement of an eye (i.e., eyeball). In each of FIGS. 24 and 25, the
reference numeral Y denotes a yellow color component. The reference
numeral C denotes a cyan color component, whereas the reference numeral M
denotes a magenta color component. It should be particularly noted that,
in FIG. 25, the number of the unit display areas A that make up the image
display area 25 are changed from that of FIG. 22 for the purpose of
practical explanation.

[0171] If the vector amount of the movement of a visual point during the
sub-field SF is smaller than the horizontal dimension of the
imaging-target object (i.e., subject image) P, images displayed during
the respective sub-fields SF overlap on the retinas of an observer. If
the images that overlap each other on the retinas of an observer
correspond to color components that differ from each other, the observer
perceives a mixed display color at the overlapping portion of the images.
In the comparative example A illustrated in FIG. 24 according to which
the single-color images of the same color component are displayed for the
entire subject image P during each sub-field SF, the observer perceives a
mixed display color out of two primary color components spanning the
width x1, which is an equivalent of the vector amount of the movement of
a visual point during the sub-field SF. For example, the observer
perceives a mixed display color of the Y component out of two primary
color components of R and G spanning the width x1, which is an equivalent
of the vector amount of the movement of a visual point during a time
period between the first sub-field SF1 in which the R component is
displayed and the second sub-field SF2 in which the G component is
displayed.

[0172] On the other hand, in the configuration of the image display device
100 according to the present embodiment C1 of the invention that is
illustrated in FIG. 25, since the display color of a single-color image
that is displayed in the unit display areas A that belong to one group
differs from a single-color image that is displayed in the unit display
areas A that belong to another group, in comparison with the comparative
example A illustrated in FIG. 24, the width x2 within which
different-color images overlap each other on the retinas of an observer
due to the instantaneous movement of a visual point becomes smaller (than
the width x1 of FIG. 24) while the frequency of the overlapping of
different-color images on the retinas of the observer due to the
instantaneous movement of the visual point becomes greater. For this
reason, with the configuration of the image display device 100 according
to the present embodiment C1 of the invention that is illustrated in
FIGS. 21, 22, 23, and 25, it becomes harder for an observer to perceive a
visible distinction between the regions of primary color components and
the regions of mixed color components in an image formed on his/her
retinas thereof, which is advantageous. Thus, in comparison with the
configuration of the comparative example A described herein, the image
display device 100 according to the present embodiment C1 of the
invention makes it possible to achieve a greater reduction in the
aforementioned color-breakup phenomenon in an image visually perceived by
a user who observes the display screen thereof.

Embodiment C2

[0173] In the foregoing exemplary embodiment C1 of the invention, it is
explained that the single-color images of three primary color components
are sequentially displayed on the basis of an input image signal S1. In
contrast, in the configuration of the image display device 100 according
to the present embodiment of the invention, as done in the foregoing
exemplary embodiment A1 of the invention, a display color specified by
the input image signal S1 is separated into a plurality of primary color
components and a plurality of white components. In the following
description of the image display device 100 according to the present
embodiment C2 of the invention, the same reference numerals are
consistently used for constituent elements thereof that have the same
operation and function as those described in the foregoing exemplary
embodiment C1 of the invention so as to omit any redundant explanation
thereof as long as the context allows.

[0174]FIG. 26 is a diagram that schematically illustrates an example of
the configuration of a display device according to an exemplary
embodiment C2 of the invention. As illustrated in FIG. 26, the image
display device 100 according to the present embodiment of the invention
is provided with, in addition to the same components as those of the
foregoing exemplary embodiment C1 of the invention, the image-processing
unit 40 as in the configuration of the image display device 100 according
to the foregoing exemplary embodiment A1 of the invention. The
image-processing unit 40 according to the present embodiment of the
invention generates a color separation image signal S2 from an input
image signal S1 that is supplied thereto from an external device that is
not shown in the drawing and then outputs the generated color separation
image signal S2. The color separation image signal S2 individually
specifies, for each of the plurality of pixels, a gradation value for
each of separated components, which are obtained in the form of a
plurality of primary-color components and a plurality of white components
as a result of the color separation of a display color that is specified
by the input image signal S1. As illustrated in FIG. 26, the color
separation image signal S2 according to the present embodiment of the
invention specifies the gradation G2_W1 of the first white component W1
and the gradation G2_W2 of the second white component W2 in addition to
the gradation G2_R of the R color component, the gradation G2_G of the G
color component, and the gradation G2_B of the B color component. The
color separation image signal S2 is generated through the same processing
as that explained above while referring to FIGS. 3, 4, and 5 in the
foregoing first exemplary embodiment A1 of the invention.

[0175]FIG. 27 is a timing chart that schematically illustrates an example
of the timing operation of the image display device 100 according to the
present embodiment of the invention. As illustrated in FIG. 27, each
frame F is time-divided into a plurality of sub-fields. In the
illustrated embodiment of the invention, one frame F is time-divided into
six sub-fields, which are denoted as SF1, SF2, SF3, SF4, SF5, and SF6.
The operations of the illumination device 10 and the illumination-device
driving circuit 52 during the sub-fields SF2, SF3, and SF4 in the present
embodiment of the invention are the same as those during the sub-fields
SF1, SF2, and SF3 in the foregoing exemplary embodiment C1 of the
invention.

[0176] The illumination-device driving circuit 52 according to the present
embodiment of the invention commands all three of the red, green, and
blue light-emitting elements 12R, 12Q and 12B provided in each of the
area illumination units B to emit light in each of the first sub-field
SF1 and the fifth sub-field SF5. As a result of such light-emission
control that is performed by the illumination-device driving circuit 52,
white light is irradiated onto all of the unit display areas A of the
liquid crystal device 20 in each of the first sub-field SF1 and the fifth
sub-field SF5. On the other hand, the illumination-device driving circuit
52 commands all three of the red, green, and blue light-emitting elements
12R, 12G, and 12B provided in each of the area illumination units B not
to emit light during the sixth sub-field SF6. Therefore, no light is
irradiated onto the liquid crystal device 20 in the sixth sub-field SF6.

[0177] The liquid-crystal-device driving circuit 54 sets the electric
potential of each of the pixel electrodes 24, which are arrayed in each
of the unit display areas A, at a data electric potential that is in
accordance with a gradation value specified by a color separation image
signal S2 for a certain primary color component R, or B (i.e., in
accordance with G2_R, G2_G, or G2_B) that should be displayed in the unit
display areas A that belong to a certain group in the writing time period
PW of each of the second, third, and fourth sub-field SF2, SF3, and SF4,
which is similar to the operation performed in the foregoing exemplary
embodiment C1. On the other hand, in the writing time period PW of the
first sub-field SF1 during which white light is irradiated onto the
liquid crystal device 20, the liquid-crystal-device driving circuit 54
supplies a data electric potential that corresponds to the gradation
G2_W1 of the W1 component to each pixel electrode 24. In like manner, in
the writing time period PW of the fifth sub-field SF5 during which white
light is irradiated onto the liquid crystal device 20, the
liquid-crystal-device driving circuit 54 supplies a data electric
potential that corresponds to the gradation G2_W2 of the W2 component to
each pixel electrode 24. In the sixth sub-field SF6 during which the
illumination device 10 switches light off so that no light should be
irradiated onto the liquid crystal device 20, the liquid-crystal-device
driving circuit 54 supplies, to each pixel electrode 24, a data electric
potential that reduces the transmission factor of liquid crystal to the
minimum value (e.g., zero).

[0178] Since the controlling unit 50 controls the operations of the
illumination device 10 and the liquid crystal device 20 as explained
above, single-color images of primary color components different from one
another are displayed in the unit display areas A that belong to the
first, second, and third groups C1, C2, and C3 respectively in each of
the second, third, and fourth sub-fields SF2, SF3, and SF4. In addition
thereto, since the controlling unit 50 controls the operations of the
illumination device 10 and the liquid crystal device 20 as explained
above, a single-color image of the first white component W1 is displayed
in all of the unit display areas A during the first sub-field SF1 that is
allocated immediately before the primary-color-component subfields SF2,
SF3, and SF4, whereas a single-color image of the second white component
W2 is displayed in all of the unit display areas A during the fifth
sub-field SF5 that is allocated immediately after the
primary-color-component subfields SF2, SF3, and SF4. In the last
sub-field SF6, a black image K is displayed in all of the unit display
areas A.

[0179] As explained above, in the configuration of the image display
device 100 according to the present embodiment of the invention, since
the first white component W1 and the second white component W2 are
extracted out of a display color of each pixel, the brightness level of a
single-color image of each of three primary color components of R, G, and
B becomes lower in comparison with that of the foregoing exemplary
embodiment C1 of the invention. Since no color breakup occurs in the
single-color image of a white component, taken in combination with the
above-described decreased (i.e., suppressed) brightness level of a
single-color image of each of three primary color components of R, and B,
the image display device 100 according to the present embodiment of the
invention makes it possible to achieve a greater reduction in the
aforementioned color-breakup image problem in an image visually perceived
by a user who observes the display screen thereof in comparison with the
image display device 100 according to the foregoing exemplary embodiment
C1 of the invention in which single-color images that correspond to
primary color components R, and B only are displayed, which means that no
single-color images that correspond to white components W1 and W2 are
displayed. In addition, in the configuration of the image display device
100 according to the present embodiment of the invention, the
non-image-display subfield SF6 during which a black K image is displayed
is allocated in each frame F in addition to the sub-fields SF2, SF3, and
SF4 during which single-color images that correspond to three primary
color components of R, G, and B are displayed in a parallel manner and
the sub-fields SF1 and SF5 during which single-color images that
correspond to the first white component W1 and the second white component
W2 respectively are displayed. Therefore, in comparison with the
configuration of the image display device 100 according to the foregoing
exemplary embodiment C1 of the invention in which no black image K is
displayed, the image display device 100 according to the present
embodiment of the invention makes it possible to achieve a greater
reduction in the aforementioned moving-picture blur phenomenon, that is,
the visual perception of the blurred outline of a moving subject image P.

[0180] Moreover, in the configuration of the image display device 100
according to the present embodiment of the invention, as has already been
explained earlier, if the combined gradation of the pre-separation
"white" component (corresponding to W1+W2), or in other words, the
minimum value Gmin, contained in a display color specified by the input
image signal S1 is greater than the threshold value TH1, the
pre-separation white component is split into the first actual white
component W1 and the second actual white component W2 at the boundary of
the threshold value TH1 in the white extraction process. Then, these
split white components are respectively displayed in separate sub-fields
SF that are "time-isolated" from each other; specifically, the first
white component W1 is displayed in the first sub-field SF1 whereas the
second white component W2 is displayed in the fifth sub-field SF5 in the
illustrated configuration thereof according to the present embodiment of
the invention. This means that a difference between the gradations of
primary-color-component single-color images and the gradations of
white-component single-color images is made smaller. Therefore, in
comparison with, for example, the configuration of the aforementioned
related art described in JP-A-2002-169515 according to which a
single-color image of a white component that is extracted from a display
color specified by an input image signal S1 is displayed in only one
sub-field SF, the image display device 100 according to the present
embodiment of the invention has an advantage in that it can reduce
flickers, which is the same non-limiting advantageous effects of the
invention as those offered by the image display device 100 according to
the foregoing exemplary embodiment A1 of the invention. Furthermore, as
is the case with the image display device 100 according to the foregoing
exemplary embodiment A1 of the invention, in the configuration of the
image display device 100 according to the present embodiment of the
invention, it is possible to offset an increase in flickers due to the
insertion of a black-image display by a decrease therein achieved by the
time-separated display of split white components.

Embodiment C3

[0181] Next, an exemplary embodiment C3 of the invention is explained
below. In the foregoing exemplary embodiment C2 of the invention, it is
explained that a single-color image of the first white component W1 is
displayed in the first sub-field SF1 whereas a single-color image of the
second white component W2 is displayed in the fifth sub-field SF5. This
means that each of a single-color image of the first white component W1
and a single-color image of the second white component W2 is displayed in
a dedicated or discreet white-component subfield (SF1 and SF5) that is
isolated from primary-color-component subfields (SF2, SF3, and SF4). In
contrast, in the configuration of the image display device 100 according
to the present embodiment C3 of the invention, both of single-color
images that correspond to three primary color components and single-color
images that correspond to a plurality of white components are displayed
without any isolation between primary-color-component subfields and
white-component subfields in a plurality of unit display areas A in a
parallel manner in each of sub-fields SF on the basis of a color
separation image signal S2 that is generated by the image-processing unit
40.

[0182]FIG. 28 is a concept diagram that schematically illustrates a
division example of an image display area 25, where the image display
area 25 is divided into a plurality of unit display areas A. As
illustrated in FIG. 28, the plurality of unit display areas A (in the
illustrated example, twenty-five unit display areas A) that make up the
image display area 25 are divided into five groups C1, C2, C3, C4, and
C5. As is the case with the array pattern of the unit display areas A
according to the foregoing exemplary embodiment C1 of the invention, one
unit display area A that belongs to a certain group C is not adjacent to
another unit display area A that belongs to the same group C as viewed
along the X direction nor along the Y direction.

[0183]FIG. 29 is a timing chart that schematically illustrates an example
of the timing operation of the image display device 100 according to the
present embodiment of the invention. As illustrated in FIG. 29, the
controlling unit 50 controls the display of each unit display area A in
each of the sub-fields SF1-SF5 in such a manner that a single-color image
of each of a plurality of components, which is five colors in the
illustrated embodiment of the invention that are made up of three primary
color components of R, G, and B and two white components of W1 and W2, is
displayed in the unit display areas A that belong to the corresponding
group C, so as to provide sequential non-isolated display. That is, the
sequential order of the display colors of single-color images that appear
in the unit display areas A that belong to one group C differs from the
sequential order of the display colors of single-color images that appear
in the unit display areas A that belong to another group C, where, in
this embodiment C3 of the invention, the display colors are made up of
five colors including the above-mentioned three primary color components
of R, G, and B and the above-mentioned two white components of W1 and W2.
For example, in the unit display areas A that belong to the first group
C1, the display colors of single-color images appear in the sequential
order of the first white component W1 (SF1), the green color component G
(SF2), the blue color component B (SF3), the second white component W2
(SF4), and the red color component R (SF5)
(W1→G→B→W2→R). In the unit display areas A
that belong to the second group C2, the display colors of single-color
images appear in the sequential order of the green color component G
(SF1), the blue color component B (SF2), the second white component W2
(SF3), the red color component R (SF4), and the first white component W1
(SF5) (G→B→W2→R→W1). As done in the foregoing
exemplary embodiment C2 of the invention, in the last sub-field SF6, a
black image K is displayed in all of the unit display areas A.

[0184] The same advantageous effects as those offered by the configuration
of the image display device 100 according to the foregoing exemplary
embodiment C2 of the invention are offered with the configuration of the
image display device 100 according to the present embodiment C3 of the
invention. In the foregoing exemplary embodiment C2 of the invention, the
primary-color-component subfields SF2, SF3, and SF4 during which
single-color images of primary color components are displayed are arrayed
in a successive manner on a time axis. In contrast, in the sub-field
configuration according to the present embodiment C3 of the invention,
the display of single-color images of primary color components does not
succeed in the unit display areas A of each group C because the display
of at least one of single-color images of white components is interposed
therebetween on the time axis. As has already been explained above, the
aforementioned problem of a color breakup is conspicuous especially if
the single-color images of a plurality of primary color components are
displayed successively on a time axis. In this respect, with the
configuration of the image display device 100 according to the present
embodiment of the invention, advantageously, it becomes harder for a user
who observes the display screen thereof to perceive the aforementioned
color-breakup image problem in comparison with the configuration of the
image display device 100 according to the foregoing exemplary embodiment
C2 of the invention in which the primary-color-component subfields SF2,
SF3, and SF4 during which single-color images of primary color components
are displayed are arrayed in a successive manner on a time axis.

[0185] As has already been explained earlier while referring to FIGS. 12,
13, and 14, the number of white components split after the extraction
thereof and the display order/positions (i.e., sub-field arrangement
order/positions) of the single-color images of white components are not
restrictively specified herein and thus may be arbitrary modified. As a
non-limiting example of the modified number of white components split
after the extraction thereof, in addition to the first white component W1
and the second white component W2, a third white component W3 may also be
extracted from a display color specified by an input image signal S1. A
plurality of the unit display areas A that makes up the image display
area 25 is divided into seven groups C1, C2, C3, C4, C5, C6, and C7. As
illustrated in FIG. 30, the controlling unit 50 controls the display of
each unit display area A in each of the sub-fields SF1-SF6 in such a
manner that a single-color image of each of a plurality of components,
which is six colors in the illustrated embodiment of the invention that
are made up of three primary color components of R, G, and B and three
white components of W1, W2, and W3, is displayed in the unit display
areas A that belong to the corresponding group C, so as to provide
sequential non-isolated display. As has already been explained earlier,
the gradation of a single-color image of each of a plurality of white
components decreases as the number of white components split after the
extraction (i.e., separation) thereof increases. Therefore, the image
display device 100 having such a modified configuration has an advantage
in that it can reduce flickers that are perceived by an observer.

[0186] A judgment as to whether (A) a single-color image that corresponds
to a certain white component is displayed in a dedicated or discreet
white-component subfield that is isolated from primary-color-component
subfields as explained in the foregoing exemplary embodiment C2 of the
invention or (B) both of single-color images that correspond to three
primary color components and a single-color image that corresponds to a
certain white component are displayed without any isolation between
primary-color-component subfields and the white-component subfield as
explained in the foregoing exemplary embodiment C3 of the invention can
be made on an individual-decision basis for each of a plurality of white
components that are extracted from a display color specified by an input
image signal S1. For example, as illustrated in FIG. 31, in the case of a
configuration example in which two white components W1 and W2 are
extracted from a display color specified by an input image signal S1,
both of single-color images that correspond to three primary color
components R, G, and B and a single-color image that corresponds to the
first white component W1 are displayed without any isolation between
primary-color-component subfields and the white-component subfield as
explained in the foregoing exemplary embodiment C3 of the invention,
whereas a single-color image that corresponds to the second white
component W2 is displayed in a dedicated or discreet white-component
subfield SF5 that is isolated from other (i.e., primary-color-component
and the first-white-component) subfields as explained in the foregoing
exemplary embodiment C2 of the invention. As another example, as
illustrated in FIG. 32, in the case of a configuration example in which
three white components W1, W2, and W3 are extracted from a display color
specified by an input image signal S1, both of single-color images that
correspond to three primary color components R, and B and single-color
images that correspond to the first white component W1 and the second
white component W2 are displayed without any isolation between
primary-color-component subfields and the white-component subfields as
explained in the foregoing exemplary embodiment C3 of the invention,
whereas a single-color image that corresponds to the third white
component W3 is displayed in a dedicated or discreet white-component
subfield SF6 that is isolated from other (i.e., primary-color-component
and the first-and-second-white-component) subfields as explained in the
foregoing exemplary embodiment C2 of the invention.

Embodiment D1

[0187]FIG. 33 is a diagram that schematically illustrates an example of
the configuration of a display device according to an exemplary
embodiment D1 of the invention. As illustrated in FIG. 33, an image
display device 100 is provided with an illumination device 10, a liquid
crystal device 20, an image-processing unit 40, a controlling unit 50,
and a brightness-level controlling unit (i.e., luminance controlling
unit) 60. The image-processing unit 40, the controlling unit 50, and the
brightness-level controlling unit 60 may be provided in a single
integrated circuit. Or, these image-processing unit 40, controlling unit
50, and brightness-level controlling unit 60 may be provided in more than
one integrated circuit in a discrete manner.

[0188] The illumination device 10 and the liquid crystal device 20
function in cooperation with each other so as to display a color image.
FIG. 34 is a timing chart that schematically illustrates an example of
the timing operations of the illumination device 10 and the liquid
crystal device 20 according to an exemplary embodiment of the invention.
As illustrated in FIG. 34, the frame F is time-divided into a plurality
of sub-fields SF. In the illustrated embodiment of the invention, one
frame F is time-divided into six sub-fields, which are denoted as SF1,
SF2, SF3, SF4, SF5, and SF6. The illumination device 10 and the liquid
crystal device 20 sequentially display a plurality of single-color
images, that is, images each of which corresponds to an individual
single-color component displayed in corresponding one of sub-fields SF.
That is, the illumination device 10 and the liquid crystal device 20
perform so-called field sequential display. A user who observes the
display screen of the image display device 100 views these single-color
images displayed in the respective sub-fields SF in a sequential manner.
As a result thereof, they visually perceive a color image that is formed
as a mixture of these individual single color components.

[0189] As illustrated in FIG. 33, an input image signal S1 is supplied
from an external device that is not shown in the drawing to the
image-processing unit 40. The input image signal 51 individually
specifies a gradation value for each of three primary color components,
that is, R color component (i.e., R component), G color component (i.e.,
G component), and B color component (i.e., B component), which make up
the display color of a pixel. The image-processing unit 40 is, as in the
configuration of the foregoing exemplary embodiment A1 of the invention,
provided with a memory circuit 42 and a separation circuit 44. Hereafter,
the term "color separation" is used with no intention to limit the scope
of the invention. The memory circuit 42 stores an input image signal S1
for each frame F. The color separation circuit 44 generates a color
separation image signal S2 from the input image signal S1 that has been
memorized in the memory circuit 42 and then outputs the generated color
separation image signal S2. As illustrated in FIG. 33, the color
separation image signal S2 according to the present embodiment of the
invention specifies the gradation G2_W1 of a first white component W1 and
the gradation G2_W2 of a second white component W2 in addition to the
gradation G2_R of the R color component, the gradation G2_G of the G
color component, and the gradation G2_B of the B color component. The
color separation image signal S2 is generated through the same processing
as that explained above while referring to FIGS. 3, 4, and 5 in the
foregoing first exemplary embodiment A1 of the invention. As has already
been explained earlier while referring to FIGS. 12, 13, and 14, the
number of white components split after the extraction thereof and the
display order/positions (i.e., sub-field arrangement order/positions) of
the single-color images of white components are not restrictively
specified herein and thus may be arbitrary modified.

[0190] The controlling unit 50 illustrated in FIG. 33 is a circuit that
drives (i.e., controls) the operations of the image display device 10 and
the liquid crystal device 20. The controlling unit 50 is provided with an
illumination-device driving circuit 52, which drives the illumination
device 10, and a liquid-crystal-device driving circuit 54, which drives
the liquid crystal device 20. The operations of the illumination-device
driving circuit 52 and the liquid-crystal-device driving circuit 54 are
the same as those explained in the foregoing exemplary embodiment A1 of
the invention.

[0191] Next, the configuration of the brightness-level controlling unit 60
and the operation thereof, which is shown in FIG. 33, are explained
below. The brightness-level controlling unit 60 is a device that controls
the entire brightness (i.e., luminance) of display performed by the image
display device 100. In the present embodiment of the invention, the
brightness-level controlling unit 60 controls the brightness (level) of
the illumination device 10. The brightness-level controlling unit 60 is
provided with a coefficient calculation sub-unit 62 and a memory sub-unit
64. The coefficient calculation sub-unit 62 of the brightness-level
controlling unit 60 calculates a correction coefficient (i.e., correction
factor) K on the basis of the input image signal S1 that is stored in the
memory circuit 42 of the image-processing unit 40. The memory sub-unit 64
of the brightness-level controlling unit 60 pre-stores a brightness curve
(i.e., luminance curve) CL, which is used for the computation of the
correction coefficient K performed by the coefficient calculation
sub-unit 62 thereof. An example of the brightness curve CL is illustrated
in FIG. 36. The brightness-level controlling unit 60 controls the
operation of the illumination-device driving circuit 52 so that the
illumination device 10 should emit light at a brightness level in
accordance with the correction coefficient K in each sub-field SF.

[0192]FIG. 35 is a flowchart that illustrates an example of the operation
of the coefficient calculation sub-unit 62 according to the present
embodiment of the invention. The processing flow illustrated in FIG. 35
is executed at each time when an input image signal S1 is memorized in
the memory circuit 42 for one frame F. FIG. 36 is a graph that shows an
example of the brightness curve CL that is stored in the memory sub-unit
64.

[0193] As illustrated in the flowchart of FIG. 35, as a first step
thereof, the coefficient calculation sub-unit 62 calculates the total sum
IA of gradation values G0 of all pixels of a display image (step SA1).
The gradation value G0 of each pixel is a value that depends on the
gradation G1_R of the R component, the gradation G1_G of the G component,
and the gradation G1_B of the B component. For example, the weighted sum
of these three gradations G1_R, G1_G, and G1_B is computed as the
gradation value G0.

[0194] In the next step, the coefficient calculation sub-unit 62
calculates an index value IB on the basis of the total sum IA calculated
in the preceding step SA1 (step SA2). The index value IB is a value that
indicates the degrees of lightness and darkness of an image in a frame F.
The ratio of the total sum (IA) to a predetermined value (mS), which is
mathematically expressed as IA/mS, is preferably adopted as the index
value IB. For example, the predetermined value mS is a total sum value IS
that is obtained under an assumption that the maximum value of the
gradation (G0) is specified for all pixels of a display image. The
maximum gradation value is a gradation that corresponds to white display.
That is, the total sum value (IS) is calculated as the result of
multiplying the total number of pixels by the maximum value of the
gradation G0. As illustrated in FIG. 36, assuming an imaging condition in
which a white rectangular subject image (e.g., window) P is displayed
against a low-gradation background such as a black background, as the
size of the subject image P increases, so does the index value IB.
Therefore, rephrasing the above, the index value IB can also be defined
as a value that indicates the area-occupation percentage of a
high-gradation subject image P in the entire region of an image display
area, that is, a value that indicates the relative size of the subject
image P.

[0195] Referring back to FIG. 35, the coefficient calculation sub-unit 62
sets the aforementioned correction coefficient K in such a manner that
the index value IB that was calculated in the preceding step SA2 and an
actual brightness of the illumination device 10 satisfy a predetermined
relationship that is expressed as the brightness curve CL (step SA3). As
shown in FIG. 36, the brightness curve CL defines the relation between
the index value IB and a brightness level (i.e., luminosity) LM in such a
manner that the brightness LM of the illumination device 10 decreases as
the index value IB increases. The coefficient calculation sub-unit 62
finds a value of the brightness LM that corresponds to the calculated
index value IB on the basis of the brightness curve CL. Then, the
coefficient calculation sub-unit 62 sets the correction coefficient K on
the basis of the identified brightness LM. As illustrated in FIG. 36, it
is assumed here that the value of the brightness LM corresponding to the
minimum value of the index IB is LM_max. It is further assumed that the
value of the brightness LM corresponding to the calculated index value IB
is LM_a. In such a case, the correction coefficient K is set at a value
that is mathematically expressed as LM_a/LM_max, that is, the ratio of
the found brightness value LM_a to the maximum brightness value LM_max.

[0196] The illumination-device driving circuit 52 illustrated in FIG. 33
controls the operation of the light-emitting element 12 (i.e., 12R, 12Q
and 12B) in such a manner that the brightness of the illumination device
10 increases as the correction coefficient K calculated by the
brightness-level controlling unit 60 increases. That is, the brightness
of the illumination device 10 increases as the number of pixels for which
high gradation is specified decreases in a display image. If this is
paraphrased, the brightness of the illumination device 10 decreases as
the number of pixels for which high gradation is specified increases in a
display image. For example, the index IB takes a small value for an image
in which minute high-gradation picture elements such as white dots are
interspersed against a low-gradation background. Since the brightness of
the illumination device 10 is high for such a small index value IB, each
of the minute picture elements is displayed in a clear manner. On the
other hand, the index IB takes a large value for an image that has high
gradation as a whole (i.e., an image having a small number of
low-gradation picture elements). Since the brightness of the illumination
device 10 is low for such a large index value IB, the power consumption
of the illumination device 10 is reduced. That is, the image display
device 100 according to the present embodiment of the invention makes it
possible to achieve high-contrast display while reducing power
consumption thereof.

[0197] In the following description, a comparative study on the occurrence
of the aforementioned color breakup image problem is conducted between
the configuration of the image display device 100 according to the
present embodiment D1 of the invention and a configuration in which the
single-color images of primary color components only are displayed in
each sub-field SF without extracting white components from an input
display color. It should be noted that such a primary-color-only-display
configuration is referred to as a "comparative example B" in the
following description. Each of FIGS. 37 and 38 is a concept diagram that
schematically illustrates an example of the formation of a perceived
image on the retinas of an observer as a result of the displaying of a
white imaging-target object (i.e., subject image) P in the configuration
of the comparative example B. Note that white is the mixed color
component that is formed as a result of the mixture of all three primary
color components. In each of FIGS. 37 and 38, it is assumed that a visual
point of a user who observes the display screen thereof moves to the
right instantaneously. Such an instant movement of a visual point is
called as a saccade, which can be further defined as, simply said, a fast
movement of an eye (i.e., eyeball). The horizontal dimension of the
displayed subject image P shown in FIG. 37 (which shows the comparative
example B) is smaller than that of the displayed subject image P shown in
FIG. 38 (which also shows the comparative example B).

[0198] If the vector amount of the movement of a visual point during the
sub-field SF is substantially equal to or smaller than the horizontal
dimension of the imaging-target object (i.e., subject image) P, as
illustrated in FIG. 37, the single-color images of primary color
components displayed during the respective sub-fields SF do not overlap
on the retinas of an observer. Therefore, the observer perceives a color
breakup, that is, an array of a plurality of primary color components, in
a conspicuous manner. On the other hand, referring to FIG. 38, if a
visual point of a user who observes the display screen thereof moves at
the substantially same speed as that of FIG. 37, since the horizontal
dimension of the displayed subject image P shown in FIG. 38 is larger
than that of the displayed subject image P shown in FIG. 37, the
single-color images of primary color components displayed during the
respective sub-fields SF overlap on the retinas of the user. Therefore,
the observer perceives a mixed display color out of two primary color
components where two of the single-color images of primary color
components overlap each other. In addition, the observer perceives mixed
white out of three primary color components where three of the
single-color images of primary color components overlap one another.
Therefore, a color breakup perceived by the observer becomes less
conspicuous in comparison with that perceived under the condition
illustrated in FIG. 37. As explained above, generally speaking, a color
breakup that is caused by field-sequential display becomes more
conspicuous as the size of the subject image P becomes smaller.

[0199] The brightness curve CL shown in FIG. 36 is prepared in such a
manner that the brightness LM of the illumination device 10 (i.e.,
display brightness) increases as the size of the subject image P that is
displayed in an image display area decreases. Therefore, if a small
subject image P is displayed in the configuration of the comparative
example B while controlling display brightness so as to satisfy the
relationship expressed as the brightness curve CL shown in FIG. 36, a
color breakup that is perceived by the observer becomes very conspicuous
because of a combination of two unfavorable reasons: that is, firstly,
there is no or little, if any, overlap of the single-color images of
primary color components displayed during the respective sub-fields SF on
the retinas of the user because of the small horizontal dimension of the
displayed subject image P; and, secondly, each of the single-color images
of primary color components is displayed at a high brightness level. In
contrast, in the configuration of the image display device 100 according
to the present embodiment D1 of the invention, a color breakup is reduced
thanks to the display of, in each frame F, the single-color images of
white components that are extracted from a display color specified by an
input image signal S1. Therefore, as a non-limiting advantage thereof,
despite the fact that the controlling of the brightness of the
illumination device 10 on the basis of the brightness curve CL could be a
cause for making a color breakup more conspicuous, the image display
device 100 according to the present embodiment D1 of the invention is
still capable of achieving a quite satisfactory reduction in the
aforementioned color-breakup phenomenon in an image visually perceived by
a user who observes the display screen thereof.

[0200] In a configuration such as that of the aforementioned related art
described in JP-A-2002-169515 according to which a single-color image of
a white component that is extracted from a display color specified by an
input image signal S1 is displayed in only one sub-field SF unlike the
present embodiment of the invention, the gradation of the single-color
image of the white component is significantly higher than that of the
single-color images of other color components especially if the display
color of an image is close to white. In addition, the brightness of the
illumination device 10 is relatively high when a white subject image P
having a relatively small size is displayed. Therefore, the gradation of
the single-color image of the white component becomes very high for these
reasons. Consequently, in the aforementioned related art described in
JP-A-2002-169515, an observer perceives conspicuous flickers because
single-color images of primary color components each having a low
gradation and a single-color image of a white component having a high
gradation are displayed in a field-sequential manner. In the
configuration of the image display device 100 according to the present
embodiment of the invention, as has already been explained earlier, if
the combined gradation of the pre-separation "white" component
(corresponding to W1+W2), or in other words, the minimum value Gmin,
contained in a display color specified by the input image signal S1 is
greater than the threshold value TH1, the pre-separation white component
is split into the first actual white component W1 and the second actual
white component W2 at the boundary of the threshold value TH1 in the
white extraction process. Then, these split white components are
respectively displayed in separate sub-fields SF that are "time-isolated"
from each other; specifically, the first white component W1 is displayed
in the first sub-field SF1 whereas the second white component W2 is
displayed in the fifth sub-field SF5 in the illustrated configuration
thereof according to the present embodiment of the invention. This means
that a difference between the gradations of primary-color-component
single-color images and the gradations of white-component single-color
images is made smaller. Therefore, in comparison with the configuration
of the aforementioned related art described in JP-A-2002-169515, the
image display device 100 according to the present embodiment of the
invention has an advantage in that it can reduce flickers, which is the
same non-limiting advantageous effects of the invention as those offered
by the image display device 100 according to the foregoing exemplary
embodiment A1 of the invention. Furthermore, as is the case with the
image display device 100 according to the foregoing exemplary embodiment
A1 of the invention, in the configuration of the image display device 100
according to the present embodiment of the invention, it is possible to
offset an increase in flickers due to the insertion of a black-image
display by a decrease therein achieved by the time-separated display of
split white components.

Embodiment D2

[0201] Next, an exemplary embodiment D2 of the invention is explained
below. In the configuration of the image display device 100 according to
the present embodiment D2 of the invention, as done in the foregoing
exemplary embodiment B1 of the invention, a single-color image of the
same color component is displayed sequentially in the plurality of unit
display areas A in each sub-field SF, or as a modification thereof, a
single-color image of different color components is displayed
sequentially therein. With such a configuration, it is possible to
effectively prevent the occurrence of the aforementioned color-breakup
image problem that is attributable to a difference between the actual
movement of a subject image P and the movement of a visual point of a
user.

[0202] The brightness-level controlling unit 60 controls the display
brightness of each of the plurality of unit display areas A in the same
manner as done in the preceding embodiment D1 of the invention. More
specifically, the coefficient calculation sub-unit 62 sets, for each of
the plurality of unit display areas A, a correction coefficient K in such
a manner that an index value IB that was calculated on the basis of the
gradation value G0 of each of pixels arrayed in the unit display area A
and the actual brightness LM of an area illumination unit B of the
illumination device 10 that corresponds to (i.e., is provided opposite
to) the unit display area A satisfy a predetermined relationship that is
expressed as a brightness curve CL.

[0203] The illumination-device driving circuit 52 controls the operation
of the light-emitting element 12 (i.e., 12R, 12G, and 12B) of each of the
area illumination units B in such a manner that the brightness of the
area illumination unit B corresponding to the unit display area A
increases as the correction coefficient K calculated for the unit display
area A by the brightness-level controlling unit 60 increases. That is,
the brightness of the area illumination unit B of the illumination device
10 increases as the number of pixels for which high gradation is
specified decreases in an image displayed in the unit display area A
corresponding to the area illumination unit B. With the above-described
configuration, the image display device 100 according to the present
embodiment D2 of the invention makes it possible to achieve high-contrast
display while reducing power consumption thereof.

[0204] Despite the fact that the controlling of the brightness of each of
the area illumination units B of the illumination device 10 on the basis
of the brightness curve CL could be a cause for making a color breakup
more conspicuous, the image display device 100 according to the present
embodiment D2 of the invention is still capable of effectively
suppressing the aforementioned color-breakup phenomenon in an image
visually perceived by a user who observes the display screen thereof
thanks to the sequential displaying of a single-color image of the same
color component in the plurality of unit display areas A in each
sub-field SF, or as a modification thereof, thanks to the sequential
displaying of a single-color image of different color components therein,
which is the same non-limiting advantageous effects of the present
embodiment of the invention as those offered by the image display device
100 according to the foregoing exemplary embodiment B1 of the invention.
Moreover, since display brightness is controlled for each of the unit
display areas A in the configuration of the image display device 100
according to the present embodiment D2 of the invention, it is possible
to satisfy both of a reduction in power consumption and a reduction in
the occurrence of the color-breakup image problem in a compatible manner
depending on the content of an image that is displayed in each of the
unit display areas A.

Embodiment D3

[0205] Next, an exemplary embodiment D3 of the invention is explained
below. In the configuration of the image display device 100 according to
the present embodiment D3 of the invention, as done in the foregoing
exemplary embodiment C1 of the invention, single-color images of color
components different from one another are displayed in the unit display
areas A, which are divided portions of the image display area 25.
Therefore, the image display device 100 according to the present
embodiment D3 of the invention makes it possible to achieve a greater
reduction in the aforementioned color-breakup phenomenon in an image
visually perceived by a user who observes the display screen thereof in
comparison with a configuration in which the single-color images of the
same color component are displayed in the entire region of the image
display area 25 during each sub-field SF of a frame F.

[0206] The brightness-level controlling unit 60 controls the display
brightness of each of the plurality of unit display areas A, that is, the
brightness of each of the plurality of area illumination units B, in the
same manner as done in the preceding embodiment D2 of the invention. That
is, the brightness of the area illumination unit B of the illumination
device 10 increases as the number of pixels for which high gradation is
specified decreases in an image displayed in the unit display area A
corresponding to the area illumination unit B. With the above-described
configuration, the image display device 100 according to the present
embodiment D3 of the invention makes it possible to achieve high-contrast
display while reducing power consumption thereof. Despite the fact that
the controlling of the brightness of each of the area illumination units
B of the illumination device 10 on the basis of the brightness curve CL
could be a cause for making a color breakup more conspicuous, the image
display device 100 according to the present embodiment D3 of the
invention is still capable of effectively suppressing the aforementioned
color-breakup phenomenon in an image visually perceived by a user who
observes the display screen thereof thanks to the parallel displaying of
single-color images of color components different from one another in the
unit display areas A, which is the same non-limiting advantageous effects
of the present embodiment of the invention as those offered by the image
display device 100 according to the foregoing exemplary embodiment C1 of
the invention. Moreover, since display brightness is controlled for each
of the unit display areas A in the configuration of the image display
device 100 according to the present embodiment D3 of the invention, it is
possible to satisfy both of a reduction in power consumption and a
reduction in the occurrence of the color-breakup image problem in a
compatible manner depending on the content of an image that is displayed
in each of the unit display areas A.

Size of Unit Display Area A

[0207] Next, the determination of an appropriate size of each unit display
area A in the foregoing exemplary embodiments B1, B2, C1, C2, D2, and D3
of the invention is explained below.

[0208]FIG. 39 is a graph that shows a relationship between the motion
velocity of the eyes of an observer and a frame frequency at which a
color breakup is not perceived by the observer. As shown in the graph of
FIG. 39, when the eyes of an observer move at a high speed, for example,
in the case of saccadic eye motion, a color breakup image problem arises
unless a frame frequency is set at a sufficiently high value. On the
other hand, if the eyes of an observer move at a low speed such as a
motion velocity value Vs or so shown in FIG. 39, the observer does not
perceive any substantial color breakup even at a not-so-high frame
frequency of 120 Hz, which is double-speed display.

[0209]FIG. 40 is a graph that shows a relationship between the moving
amount of a line of sight and the motion velocity of the eyes of an
observer. In this graph, the moving amount of a line of vision is shown
in the unit of an angular distance, that is, degrees. As shown in the
graph of FIG. 40, the motion velocity of the eyes of an observer
increases as the moving amount of a line of sight increases. For example,
as shown therein, if the moving amount of a line of sight of an observer
is approximately 10°, the motion velocity of the eyes of the
observer takes the above-described value Vs at which the observer does
not perceive a color breakup even at a double-speed (i.e., low) frame
frequency of 120 Hz. That is, if the moving amount of a line of sight is
ten degrees or less, an observer perceives almost no color breakup.
Therefore, in the present embodiment of the invention, the dimension of
each of the unit display areas A is determined while ensuring that the
moving amount of a line of sight of an observer in each thereof is ten
degrees or less.

[0210]FIG. 41 is a diagram that schematically illustrates an example of a
positional relationship between the image display area 25 and the eye E
of an observer. A normal distance between the image display area 25 and
the eye E of an observer does not exceed a value that is obtained as the
result of multiplying the dimension of a short side, which is typically a
height, of the image display area 25 by approximately six. That is, if
the short side (e.g., height) of the image display area 25 is denoted as
H as shown therein, a normal distance between the image display area 25
and the eye E of an observer does not exceed 6H. Therefore, the X-axis
dimension (or Y-axis dimension) of the unit display area A is defined as,
as illustrated in FIG. 41, the dimension (i.e., length) D1 of the base of
an isosceles triangle T1 that has the vertex angle of 10° and the
height of 6H. Preferably, the vertex angle of the isosceles triangle T1
should be 5°. Assuming a case where the eye E of an observer can
sometimes approach the image display area 25 in such a manner that the
distance between the image display area 25 and the eye E of an observer
becomes as close as three times of the short side H of the image display
area 25, the X-axis dimension (or Y-axis dimension) of the unit display
area A should be defined as, as illustrated in FIG. 41, the length D2 of
the base of an isosceles triangle T2 that has the vertex angle of
10° and the height of 3H. Preferably, the vertex angle of the
isosceles triangle T2 should be 5°. To sum up, at least one of the
X-axis dimension and the Y-axis dimension of the unit display area A
should be set at a value that is not greater than the length D1 of the
base of the isosceles triangle T1 that has the height of 6H illustrated
in FIG. 41. More preferably, at least one of the X-axis dimension and the
Y-axis dimension of the unit display area A should be set at a value that
is not greater than the length D2 of the base of the isosceles triangle
T2 that has the height of 3H illustrated in FIG. 41.

[0211] If the dimension of each of the unit display areas A having the
same size as those of others is determined as described above, the moving
amount of a line of sight of an observer never exceeds 10° in each
one of the unit display areas A. Therefore, advantageously, it is
possible to effectively prevent the occurrence of the aforementioned
color-breakup image problem while avoiding any excessive heightening of a
frame frequency. Rephrasing the above, with such a size determination, if
the moving amount of a line of sight of an observer exceeds 10°,
it follows that a visual point of the observer moves to another unit
display area A. Therefore, in combination with the above-described
configuration of the invention according to which single-color images are
displayed in the unit display areas A during the respective sub-fields SF
in a sequential manner, the unit-display-area size determination
described herein makes it possible to suppress the aforementioned
color-breakup image problem in each image visually perceived by a user
who observes the display screen thereof.

[0212] It should be noted that a method for determining the size of the
unit display area A is not limited to a specific example described above.
For example, the number M of the unit display areas A that belong to each
of the afore-mentioned first image display sub-area G1 and the
afore-mentioned second image display sub-area G2 may be determined from
the viewpoint of a color breakup reduction. As shown in FIG. 39, it is
necessary to heighten a frame frequency in order to overcome a color
breakup image problem when the motion velocity of the eyes of an observer
is high. It is assumed here for the purpose of explanation that an
NP-speed display is required for overcoming a color breakup image
problem. The time length of a frame F at a standard frame frequency of 60
Hz is denoted as T (T=16.6 ms). In order to simplify explanation, the
writing time period PW of each sub-field SF is ignored. Then, the time
length of each of the display time periods P1, P2, and P3 thereof is
expressed as approximately T/3 NP.

[0213] On the other hand, it is assumed here that the image display area
25 is divided into the M number of the unit display areas A as viewed
along the X direction. It is further assumed that an N-speed display is
performed. In order to simplify explanation, the writing time period PW
of each sub-field SF is ignored. Then, the time length of each of the
display time periods P1, P2, and P3 thereof is expressed as approximately
T/3 NM. Therefore, if T/3 NP takes the same value as T/3 NM, it is
possible to make the time length of each of the display time periods P1,
P2, and P3 thereof equal to the time length thereof under the NP-speed
display as a result of the division of the image display area 25 into the
M number of the unit display areas A as viewed along the X direction.
Thus, the number of divisions M that makes it possible to overcome a
color breakup image problem is calculated by means of the following
mathematical formula: M=NP/N. That is, the X-dimension of the unit
display area A is mathematically expressed as 1/M of the X-dimension of
the image display area 25. As explained above, it is possible to
effectively prevent the occurrence of a color-breakup image problem by
calculating the number of divisions (and thus the size of each thereof)
of the unit display areas A in such a manner that the cycle of
single-color image display in the unit display area A equals a cycle
corresponding to the NP-speed display (i.e., a cycle corresponding to a
predetermined frame frequency), which constitutes a non-limiting
alternative method of the unit-display-area size determination described
herein.

VARIATION EXAMPLES

[0214] Various kinds of changes, modifications, adaptations, variations,
improvements, or the like may be made on the specific examples of the
exemplary embodiments of the invention described above. Non-limiting
variation examples thereof are described below. Note that any two or more
of the following variation examples/modes can be combined with each other
or one another.

(1) Variation Example 1

[0215] In each of the foregoing exemplary embodiments of the invention, it
is assumed that each of the sub-fields SF that make up a frame F has the
same time length as that of others. However, the scope of the invention
is not limited to such an exemplary configuration. That is, the time
length of each sub-field SF may be changed arbitrarily. For example, the
time length of a black sub-field SF during which a black (K) image is
displayed may be set at a value greater than the time length of other
sub-fields SF, which is explained below as a first variation mode 1. As
another variation example thereof, the time length of a first white
sub-field SF during which a single-color image corresponding to a first
white component W1 is displayed and/or the time length of a second white
sub-field SF during which a single-color image corresponding to a second
white component W2 is displayed may be set at a value greater than the
time length of other sub-fields SF, which is explained below as a second
variation mode 2. These variation modes are explained in detail below.

(a) Variation Mode 1

[0216]FIG. 42 is a timing chart that schematically illustrates an example
of sub-fields SF according to the first variation mode 1. As shown in
FIG. 42, in the sub-field configuration of each frame F, the black
sub-field SF6 during which a black image K is displayed is longer than
the primary-color-component sub-fields SF2, SF3, and SF4 during which
single-color images of primary color components are displayed and the
white-component sub-fields SF1 and SF5 during which single-color images
of white components are displayed.

[0217]FIG. 43 is a concept diagram that schematically illustrates an
example of a change in display color that occurs as time elapses with the
sub-field time-length configuration of the first variation mode 1 when
the movement of a subject image P illustrated in FIG. 6 is monitored as
illustrated in FIGS. 7 and 8. As shown in FIG. 43, in comparison with a
sub-field configuration in which an equal time length is allocated for
each of sub-fields SF1-SF6, a time length Ta during which single-color
images of primary color components are displayed under the sub-field
configuration of the first variation mode 1 is shorter. For this reason,
if the sub-field configuration of the first variation mode 1 is adopted,
as illustrated in FIG. 43, the aforementioned color breakup width CA,
which indicates a range in which a user perceives a color breakup,
becomes smaller in comparison with that illustrated in FIG. 8. Moreover,
in comparison with the sub-field configuration in which an equal time
length is allocated for each of sub-fields SF1-SF6, a time length Tb
during which single-color images of primary color components and
single-color images of white components are displayed under the sub-field
configuration of the first variation mode 1 is shorter by an increase in
the time length of the black sub-field SF6. For this reason, if the
sub-field configuration of the first variation mode 1 is adopted, as
illustrated in FIG. 43, the aforementioned moving-picture blur width CB,
which indicates a range in which a moving-picture blur is perceived,
becomes smaller in comparison with that illustrated in FIG. 8.

[0218] Disadvantageously, however, flickers become more conspicuous to the
eyes of an observer if the time length of the black sub-field SF6 during
which a black image K is displayed is set at an excessively great value.
For this reason, the time length of the black sub-field SF6 should be set
at a time-percentage value smaller than 50% of each frame F. More
preferably, the time length of the black sub-field SF6 should be set at a
time-percentage value smaller than 30% thereof. On the contrary, if a
higher priority should be given to a reduction in flickers due to the
display of a black (K) image, it is preferable to adopt a configuration
in which the time length of the black sub-field SF6 is equal to that of
other sub-fields SF1-SF5. Or, in order to reduce flickers, the black
sub-field SF6 can be omitted. In the explanation of the first variation
mode 1 given above, the lengthening of the black K sub-field SF is
applied to the foregoing exemplary embodiment A1 illustrated in FIG. 1.
Notwithstanding the above, the same modification, that is, the
lengthening of the black K sub-field SF, may be applied to any other
foregoing exemplary embodiment of the invention.

(b) Variation Mode 2

[0219]FIG. 44 is a timing chart that schematically illustrates an example
of sub-fields SF according to the second variation mode 2. As shown in
FIG. 44, the fifth sub-field SF5 during which a single-color image of the
second white component W2 is displayed has a time length greater than
that of other sub-fields SF1, SF2, SF3, SF4, and SF6.

[0220]FIG. 45 is a concept diagram that schematically illustrates an
example of a change in display color that occurs as time elapses with the
sub-field time-length configuration of the second variation mode 2 when
the movement of a subject image P illustrated in FIG. 6 is monitored as
illustrated in FIGS. 7 and 8. As shown in FIG. 45, in comparison with a
sub-field configuration in which an equal time length is allocated for
each of sub-fields SF1-SF6, the time length Ta during which single-color
images of primary color components are displayed under the sub-field
configuration of the second variation mode 2 is shorter as is the case
with the first variation mode 1 described above. For this reason, if the
sub-field configuration of the second variation mode 2 is adopted, the
color breakup width CA becomes smaller in comparison with that
illustrated in FIG. 8. On the other hand, since the time length of the
black sub-field SF6 during which a black image K is displayed under the
second variation mode 2 is shorter than that of the first variation mode
1. Therefore, considering from the viewpoint of a reduction in the
moving-picture blur width CB only, the first variation mode 1 is
advantageous over the second variation mode 2. However, the lengthening
of the second white sub-field SF5 for the second white component W2,
which means or requires a shorter black sub-field SF6, is equivalent to
the increasing of a light-emission duty. Therefore, the second variation
mode 2 is advantageous over the first variation mode 1 in that it can
offer a greater reduction in flickers.

[0221] In the explanation of the second variation mode 2 given above while
referring to FIGS. 44 and 45, the time length of the second sub-field SF5
during which a single-color image corresponding to the second white
component W2 is displayed is set at a greater value. Notwithstanding the
above, the time length of the first sub-field SF1 during which a
single-color image corresponding to the first white component W1 is
displayed may be set at a greater value either in place of or in addition
to the lengthening of the second white sub-field SF5 for the second white
component W2. In the explanation of the second variation mode 2 given
above, the lengthening of the white-component sub-field SF is applied to
the foregoing exemplary embodiment A1 illustrated in FIG. 1.
Notwithstanding the above, the same modification, that is, the
lengthening of the white-component sub-field SF, may be applied to any
other foregoing exemplary embodiment of the invention.

(2) Variation Example 2

[0222] In each of the foregoing exemplary embodiments of the invention
(especially, in the embodiments B1, B2, C1, C2, D1, D2, and D3), the
display color of each of the pixels may be separated into a plurality of
color components and a plurality of white components, where the color
components include a mixed color component (cyan, magenta, or yellow), as
done in the foregoing exemplary embodiment A2 of the invention.

(3) Variation Example 3

[0223] In each of the foregoing exemplary embodiments of the invention
(especially, in the embodiments A1, A2, B2, and C2), it is explained that
the single-color images of white components W1 and W2 are displayed in
white sub-fields SF allocated immediately before and after color
sub-fields SF during which single-color images of color components, which
means either primary color components or a combination of primary color
components and mixed color components, are displayed. Notwithstanding the
foregoing, the sequential order of these white sub-fields SF and color
sub-fields SF may be arbitrarily modified. As a non-limiting modification
example thereof, as illustrated in FIG. 46, the first white sub-field
(SF2) during which the single-color image of the first white component W1
is displayed may be interposed between the red sub-field (SF1) during
which the single-color image of the red component R is displayed and the
green sub-field (SF3) during which the single-color image of the green
component G is displayed. As another non-limiting modification example
thereof, as illustrated in FIG. 47, the second white sub-field (SF4)
during which the single-color image of the second white component W2 is
displayed may be interposed between the green sub-field (SF3) during
which the single-color image of the green component G is displayed and
the blue sub-field (SF5) during which the single-color image of the blue
component B is displayed. As still another non-limiting modification
example thereof, as illustrated in FIG. 48, it is preferable to adopt a
combination of the above-described modification examples illustrated in
FIGS. 46 and 47 in which each of the first white sub-field and the second
white sub-field is interposed between two primary-color subfields. With a
modified configuration illustrated in any of FIGS. 46, 47, and 48,
primary-color-component subfields during which single-color images of
primary color components are displayed are distanced from each other or
one another on a time axis with at least one white-component subfield
being interposed therebetween. Therefore, in comparison with a sub-field
configuration in which the primary-color subfields are allocated in a
successive manner on the time axis, it becomes harder for a user who
observes the display screen thereof to perceive the aforementioned
color-breakup image problem.

(4) Variation Example 4

[0224] In each of the foregoing exemplary embodiments of the invention, it
is explained that the illumination-device driving circuit 52 controls the
illumination device 10 so as not to emit light in the last sub-field SF
of each frame F. In addition thereto, in this last sub-field SF, the
liquid-crystal-device driving circuit 54 supplies, to each pixel
electrode 24, a data electric potential that reduces the transmission
factor of liquid crystal to the minimum value. The aforementioned black
(K) image is displayed, or in other words, display is suspended, as a
result of the combination thereof. However, the scope of the invention is
not limited to such an exemplary configuration. For example, either one
of these may be performed in the last black sub-field SF. The black image
K may be displayed at the first sub-field SF of each frame F. It should
be noted that, in the above-described preferable exemplary configurations
of the invention, the position of black sub-field allocated in each frame
F and the display method of a black image K are not restrictively
specified as long as display is suspended during a certain time period in
the frame. As the word "preferable" suggests, such a black sub-field
during which a black image K is displayed may be omitted.

(5) Variation Example 5

[0225] In each of the foregoing exemplary embodiments of the invention, it
is explained that the light-emitting elements 12 (12R, 12G, and 12B)
corresponding to respective primary color components are driven (i.e.,
operated) in combination of any two thereof so as to emit mixed-color
light and/or in combination of all three thereof so as to emit white
light onto the liquid crystal device 20. However, the scope of the
invention is not limited to such an exemplary configuration. For example,
the illumination device 10 may be provided with, in addition to
primary-color-component light-emitting elements, mixed-color-component
light-emitting elements and a white-component light-emitting element.

Applications

[0226] Next, an explanation is given below of a few non-limiting examples
of a variety of electronic apparatuses to which an image display device
according to an exemplary embodiment of the invention is applicable. Each
of FIGS. 49, 50, and 51 shows an electronic apparatus that adopts the
image display device 100 according to any of the exemplary embodiments of
the invention described above, including variation examples and
modifications thereof.

[0227]FIG. 49 is a perspective view that schematically illustrates an
example of the configuration of a mobile personal computer that adopts
the image display device 100 according to an exemplary embodiment of the
invention. As illustrated in the drawing, a personal computer 2000 is
made up of, though not limited thereto, a display unit that displays a
variety of images to which the image display device 100 according to the
foregoing exemplary embodiments of the invention is applied and a
computer main assembly 2010 that is provided with a power switch 2001 and
a keyboard 2002.

[0228]FIG. 50 is a perspective view that schematically illustrates an
example of the configuration of a mobile phone to which the image display
device 100 according to an exemplary embodiment of the invention is
applied. As illustrated in the drawing, a mobile phone 3000 is provided
with, though not limited thereto, a display unit that displays a variety
of images to which the image display device 100 according to the
foregoing exemplary embodiments of the invention is applied as well as a
plurality of manual operation buttons 3001 and scroll buttons 3002. As a
user manipulates the scroll buttons 3002, content displayed on the screen
of the image display device 100 is scrolled.

[0229]FIG. 51 is a perspective view that schematically illustrates an
example of the configuration of a personal digital assistant (PDA) that
adopts the image display device 100 according to an exemplary embodiment
of the invention. As illustrated in the drawing, a personal digital
assistant 4000 is provided with, though not limited thereto, a display
unit that displays a variety of images to which the image display device
100 according to the foregoing exemplary embodiments of the invention is
applied as well as a plurality of manual operation buttons 4001 and a
power switch 4002. As a user manipulates the power switch 4002, various
kinds of information including but not limited to an address list or a
schedule table is displayed on the image display device 100.

[0230] Among a variety of electronic apparatuses to which the display
device according to the present invention is applicable are, other than
the specific examples illustrated in FIGS. 49-51, a digital still camera,
a television, a video camera, a car navigation device, a pager, an
electronic personal organizer, an electronic paper, an electronic
calculator, a word processor, a workstation, a videophone, a POS
terminal, a printer, a scanner, a copier, a video player, a touch-panel
device, and so forth.